JP2010059555A - Low-density composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-density composite material having designability and various functionalities in spite of being a low-density composite material applying a foamable microcapsule to sheet-like materials, by preventing machine stain caused by drop of the foamable microcapsule from the surface and combining low-density paper with various sheet-like materials. <P>SOLUTION: The low-density composite material is obtained by laminating sheet-like materials 2 that do not contain a foamable microcapsule and mainly includes papermaking fibers to both sides of a sheet-like material 1 that contains an unfoamed foamable microcapsule and mainly includes papermaking fibers to give a laminate 3 and then heating the laminate to foam the foamable microcapsule. The outermost layers thereof are combined with various sheet-like materials 5 to add their characteristics to the low-density composite material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a low density composite. Specifically, the present invention relates to a low-density composite having various functions such as design properties, dimensional stability, water resistance, and flame retardancy.

  Conventionally, a method for reducing the density by applying foamable microcapsules to a sheet-like material mainly made of papermaking fibers has been proposed. For example, as described in Patent Document 1 and Patent Document 2, foamable microcapsules are internally added to papermaking pulp, and the amount of water after heat foaming is considerably larger than the amount of water in general papermaking. There has been proposed a method for obtaining a bulky and lightweight paper by heating and foaming a foamable microcapsule.

  In Patent Document 3 and Patent Document 4, a paper base having a water content of 50 to 60% by weight, which is made by mixing foamable microcapsules with a papermaking raw material mainly composed of papermaking pulp, is mainly used for foamable microcapsules. The impregnating liquid comprising a capsule and a rubber latex and / or a synthetic resin emulsion is impregnated with a wet impregnation method in an amount of 5 to 40% by weight with respect to a papermaking raw material, and then the foamable microcapsule is foamed by heating. A method for producing low density paper has been proposed.

  However, the low density foamed papers described in Patent Documents 1 to 4 are mainly composed of foamable microcapsules and the entire paper layer is made porous. As a result of hindering the bonding, the paper strength and the peel strength between the paper layers are greatly reduced, and there is a problem that they are easily torn or torn. In addition, since it is necessary to foam in the state of loose hydrogen bonds before the hydrogen bonds between pulp fibers are completed, it is necessary to foam the microcapsules from a state where the moisture content in the wet paper is large, which is efficient Was also inefficient. In particular, in the examples of Patent Document 1 and Patent Document 2, since foamable microcapsules are directly mixed with pulp as a raw material, foaming occurs between poor yield in papermaking and a blanket in contact with a drying dryer. Since the microcapsules fall off from the web to the blanket, there is a drawback that the paper machine is contaminated.

  Further, in the methods of Patent Document 3 and Patent Document 4, rubber latex or synthetic resin emulsion is used in order to give a certain flexibility and strength even when a large amount of voids are generated between the paper layers after the microcapsule is foamed. The impregnation liquid was added by the wet impregnation method, and the purpose was achieved, but for that purpose, it was necessary to use a special device called a wet impregnation machine, and it could not be applied to a general paper machine. .

  Patent Document 5 discloses a foamed paper manufacturing method in which a dispersion of foamable microcapsules is sprayed on wet paper obtained by making pulp in a wire part of a paper machine. Patent Document 6 discloses wood pulp. We propose a foam base paper for ink-jet recording, in which a foamed microcapsule dispersion is spray-coated on wet paper that has been made from the main material, the foamable microcapsules are distributed in the paper layer, and the size is adjusted to a certain range. Has been. However, each of the foamed papers described in Patent Document 5 and Patent Document 6 is obtained by spraying a dispersion of foamable microcapsules onto a wet paper that has a large amount of moisture during the paper manufacturing process. Basically, the foamable microcapsules are distributed not on the paper surface but on the paper layer, and the microballoons in which the microcapsules are foamed hinders the bonding between pulp fibers, resulting in low paper strength and peel strength between the paper layers. That is, the risk of falling off the foamable microcapsules in the drying dryer is inherent as in Patent Documents 1 and 2.

  Patent Document 7 proposes a method for producing a bulky paper in which a paper base obtained by mixing pulp and foamable microcapsules is foamed by passing hot water of 90 ° C. or higher. This method has the merit that foamable microcapsules can be foamed at a time using high-density thermal energy called hot water, but it is necessary to add water to the paper web once dried through hot water again. There was a problem that drying had to be performed again.

  Patent Document 8 proposes that a foaming microcapsule is foamed by applying a coating liquid composed of a foaming microcapsule and a binder to at least one surface of a base paper and then heating it. However, a large amount of binder is required to fix the added amount of the foamable microcapsules until the required low density is obtained on the base paper surface. The use of capsules is not cost effective, and there is a problem that it takes time to foam after coating.

  As methods for obtaining low-density paper without using foamable microcapsules, Patent Document 9 and Patent Document 10 propose a method for obtaining low-density paper using a curled fiber having a specific curl factor. ing. Patent Document 11 proposes a bulky paper blended with hollow spherical satellite-type calcium carbonate. However, these proposals have problems that even if they have bulkiness, the adhesion between fibers is weak, delamination tends to occur, and paper dust is often generated during handling.

  Low density paper, foamed paper, and bulky paper as described above have many uses such as cushioning materials, heat insulating materials, and board paper, and until design and functionality such as design properties, water resistance, and flame resistance are required. The situation was not reached.

JP-A-5-339898 JP-A-10-88495 JP-A-7-243196 JP-A-8-226097 JP 2001-98494 A JP 2002-46342 A JP-A-5-230798 JP 2008-127703 A JP-A-10-212690 Japanese Patent Laid-Open No. 10-919588 Japanese Patent Laid-Open No. 3-124895

This invention makes it a subject to solve the above problems, although it is a low density composite which applied the foamable microcapsule. That is, the problems in the present invention are as follows.
(1) Prevents machine contamination due to dropping from the surface of the foamable microcapsules.
(2) Designability and various functionalities are imparted by combining low-density paper and various sheet-like materials.

  That is, the invention according to claim 1 of the present invention does not contain foamable microcapsules on both sides of a sheet-like material (1) mainly composed of papermaking fibers, including unfoamed foamable microcapsules. A low-density composite (1), wherein the foamable microcapsule is foamed by separately heating a laminate (3) obtained by laminating a sheet-like product (2) comprising fibers and drying it. 4).

  That is, in the invention according to claim 2 of the present invention, the sheet (5) is bonded to at least one surface of the laminate (3) to form a laminate (6), and then the foam is obtained by heating the laminate (6). The low-density composite (7) according to claim 1, wherein the conductive microcapsule is foamed.

  That is, the invention according to claim 3 of the present invention is characterized in that the sheet-like material (5) is bonded to at least one surface of the low-density composite (4). It is a composite (7).

  That is, the invention according to claim 4 of the present invention is characterized in that the sheet-like material (5) is any one or more selected from metal foil, resin film, paper, cloth, and nonwoven fabric. 2 or a low density composite (7) according to claim 3.

  That is, the invention according to claim 5 of the present invention is characterized in that the sheet-like material (1) is internally added and / or impregnated with an adhesive. It is a low density composite.

  That is, the invention according to claim 6 of the present invention is the low-density composite according to any one of claims 1 to 5, wherein the binder fiber is internally added to the sheet-like material (1). is there.

  That is, the invention according to claim 7 of the present invention is the low-density composite according to any one of claims 1 to 6, wherein the outer shell of the foamable microcapsule is an acrylic resin. .

  That is, in the invention according to claim 8 of the present invention, the foaming microcapsule has a foaming start temperature of 120 ° C. or higher, and the low-density composite according to any one of claims 1 to 7 It is.

  That is, in the invention according to claim 9 of the present invention, the amount of the foamable microcapsules contained in the sheet-like material (1) is 5 parts by mass or more and less than 40 parts by mass with respect to the sheet-like material (1). The low-density composite according to any one of claims 1 to 8, wherein

  The low density composite according to the present invention heats and foams the foamable microcapsules to reduce the density of the material itself, thereby exhibiting effects such as weight reduction, cushioning, and heat insulation, and various sheet-like materials on the surface. By combining them, various design properties can be obtained, or various functions such as flame retardancy, surface smoothness, water resistance, moisture permeation resistance, etc. can be given, such as building materials, stationery, packaging materials, various industrial materials, etc. It can be used effectively for applications.

In the present invention, the sheet-like material (2) mainly composed of paper-making fibers not containing foamable microcapsules on both sides of the sheet-like material (1) mainly composed of paper-making fibers, including unfoamed foamable microcapsules. Need to be laminated. The purpose of this is to prevent unfoamed foaming microcapsules present on the surface of the sheet-like material (1) from falling in the paper machine and contaminating the machine. In addition, it is necessary to heat the laminate (3) obtained thereby later, which makes it possible to foam the foamable microcapsules when necessary, thereby forming the low-density composite (4). Obtainable. The basis weight of the sheet-like product (1) is preferably 50 g / m ² or more and less than 600 g / m ² . When the basis weight is 600 g / m ² or more, heat is not transferred to the inside of the paper layer during the heat treatment, resulting in poor foaming. On the other hand, when the basis weight is less than 50 g / m ² , the thickness after foaming is poor, and heat insulation and cushioning properties are reduced. Since the effect is insufficient, it is not preferable. Further, the basis weight of the sheet-like material (2) is preferably 20 g / m ² or more and less than 200 g / m ² . If the basis weight is 200 g / m ² or more, the weight reduction of the entire sheet is impaired. Conversely, if the basis weight is less than 20 g / m ² , the papermaking efficiency is lowered, which is not preferable.

  In the present invention, papermaking fibers are mainly used. “Mainly” indicates that the mixing ratio of the fiber for papermaking accounts for 60% by mass or more of the whole. If it is less than 60% by mass, the gap between the layers of the sheet-like material is reduced, and the effect of promoting the lowering of the density of the sheet-like material (1) due to foaming of the foamable microcapsules is reduced. Also in the sheet-like material (2), if the papermaking fiber is less than 60% by mass, the generation of paper dust increases, which is not preferable. The beating degree of the papermaking fiber was 200 mlc. s. f. 550 ml c. s. f. It is preferable that it is less than. More preferably 350 ml c. s. f. 500 mlc. s. f. Is less than. The beating degree is 200 mlc. s. f. If it is less than the range, the entanglement of the fine fibers becomes large, the strength between the paper layers becomes strong, and it is not preferable because it hinders the expansion of the paper layers when foaming the microcapsules. The beating degree is 550 ml c. s. f. Exceeding this is not preferable because the strength between the paper layers becomes weak.

  Wood pulp is preferably used as the papermaking fiber. For example, wood pulp such as softwood bleached kraft pulp (NBKP), hardwood bleached kraft pulp (LBKP), softwood bleached sulfite pulp (NBSP), hardwood bleached sulfite pulp (LBSP), thermomechanical pulp (TMP), etc., alone or mixed Things can be used. Mainly made of this wood pulp, and if necessary, non-wood pulp such as hemp, bamboo, straw, kenaf, bagasse, straw, three straw and cotton, modified pulp such as cationized pulp, mercerized pulp, rayon, vinylon, Recycled fibers such as nylon, acrylic and polyester, synthetic fibers, semi-synthetic fibers, inorganic fibers such as alumina fibers and alumina silicate fibers, or microfibrillated pulp can be used alone or in combination.

  In the present invention, various sheet-like materials (5) are formed on at least one side of the low-density composite (3) in which the foamable microcapsules are not foamed or the low-density composite (4) after the foamable microcapsules are foamed. It is preferable to bond. By changing the type of the sheet-like material (5), various properties of the sheet-like material (5) itself can be imparted to the low-density composite. As the sheet-like material (5), various types of paper (there is no particular limitation as paper, for example, high-quality paper, printing paper, colored pattern paper, embossed pattern paper, decorative paper, etc.), non-woven fabric (particularly as a non-woven fabric). Examples include, but are not limited to, those manufactured by dry, wet, and direct methods using materials such as rayon, vinylon, nylon, acrylic, polyester, cotton, pulp, hemp, wool, and glass fiber. (The cloth is not particularly limited, and examples thereof include cloths such as cotton, hemp, nylon, rayon, polyester, acrylic, and woven fabrics), films (there are no particular restrictions on the film, for example, polyester resins, Polyethylene terephthalate resin, diacetate resin, triatesate resin, acrylic resin, polycarbonate resin, polyvinyl chloride Fat, polyimide resin, cellophane, celluloid, and the like.), Etc. By using various shades, it is possible to change the pattern, the touch and the like. For example, colored design paper, embossed pattern paper, decorative paper, and the like may be selected to impart design properties. Moreover, moisture resistance and water resistance can be provided by using films having moisture resistance and water resistance. Further, by using various metal foils, rigidity, flame retardancy, processing suitability such as bending, and the like can be imparted. As metal foil, arbitrary things, such as aluminum, iron, stainless steel, copper, and tin, can be used as needed. Furthermore, it is also possible to paste different sheet-like objects (5) on the front and back.

In the present invention, in order to paste the sheet (5), an aqueous adhesive such as polyvinyl alcohol, various starches, polyvinyl pyrrolidone, SBR emulsion, NBR emulsion, acrylic emulsion, vinyl acetate, etc., or a solvent-based adhesive, For example, an adhesive such as vinyl chloride resin, rubber such as chloroprene, urethane, or the like, or a solventless type epoxy or cyanoacrylate adhesive can be freely selected depending on the purpose. As the laminator, a wet laminator or a dry laminator can be freely selected depending on the adhesive used. The coating amount of the adhesive is preferably 1 g / m ² or more and less than 10 g / m ² . More preferably, it is 2 g / m ² or more and less than 8 g / m ² . If the coating amount is 10 g / m ² or more, the adhesive strength exceeds the threshold value, which is useless. If it is less than 1 g / m ² , the adhesive strength is insufficient, and peeling is not preferable. Alternatively, bonding with an extrusion laminator using a resin such as polyethylene or polypropylene is also possible. In the case of an extrusion laminator, the film thickness is preferably 3 μm or more and less than 20 μm. More preferably, it is 5 μm or more and less than 10 μm. If it is 20 μm or more, the effect of enhancing the adhesive force will reach its peak, and if it is less than 5 μm, it will be difficult to bond properly. When using a water-based adhesive, it is preferable to apply a sizing agent to the sheet-like material (1) and / or to add it internally. When a solvent-based adhesive is used, it is preferable to perform anchor coating such as polyvinyl alcohol on the adhesive-coated surface of the sheet-like material (1). By doing in this way, it can prevent that an adhesive agent osmose | permeates the inside of a sheet-like object (1), and the amount of adhesive agents with respect to a to-be-adhered object runs short.

  In the present invention, it is preferable to internally add and / or impregnate an adhesive to the sheet-like material (1), or internally add binder fibers, or both. The sheet-like material (1) is mainly composed of papermaking fibers and foamable microcapsules, and there is a risk that the paper interlayer strength of the papermaking fibers is weakened by foaming the foamable microcapsules. Therefore, by performing the operations as described above, it is possible to prevent these problems, increase the paper interlayer strength, and correct physical strength such as folding suitability. As the adhesive, an adhesive generally used for papermaking, for example, latex emulsion such as SBR and NBR, acrylic emulsion, vinyl acetate, polyvinyl alcohol, starch, modified starch, oxidized starch, polyvinylpyrrolidone and the like One or more adhesives can be used. As the usage-amount of an adhesive agent, 3 to 30 mass% is preferable as solid content of an adhesive agent. More preferably, it is 5 mass% or more and less than 25 mass%. When it is 30% by mass or more, when the laminated sheet-like material (3) or (6) is heated and foamed, the strength between the paper layers becomes too strong to inhibit foaming of the foamable microcapsules, which is not preferable. On the other hand, if it is less than 3% by mass, the effect of reinforcing the strength between the paper layers decreases, which is not preferable. The glass transition temperature (Tg) of the adhesive is preferably −35 ° C. or more and less than 80 ° C. More preferably, it is -20 degreeC or more and less than 50 degreeC. When the Tg is 80 ° C. or higher, the laminated sheet-like materials (3), (4), and (5) become hard and adversely affect elasticity and bendability. Moreover, since Tg is less than -35 degreeC, since the surface of the laminated | stacked sheet-like material (3), (4), (5) becomes sticky and it becomes easy to block, it is unpreferable.

  As the binder fiber, a binder fiber used for papermaking or nonwoven fabric can be preferably used. For example, polyethylene fiber, polypropylene fiber, polyester fiber, acrylonitrile fiber, nylon fiber, vinylon fiber, or a binder fiber having a core-sheath type double structure with a high melting point component in the core and a low melting point component in the sheath, etc. More than one type can be used. The addition amount of the binder fiber is preferably 97: 3 to 80:20 by mass ratio with respect to the sheet-like material (1). More preferably, it is 95: 5-90: 10. If the mixing ratio of the binder fiber to the sheet-like material (1) is 20% or more, the binder effect reaches its peak, which is not preferable because it is not economical, and if it is less than 3%, the effect of reinforcing the paper interlayer strength is reduced. Absent.

  In the present invention, as a method of foaming the foamable microcapsules by separately heating the laminate (3) or the laminate (6), it may be passed through a heated oven or hot air may be applied. Although possible, it is preferred to pass between heated rolls because it is efficient. As the material of the roll, it is preferable to use a metal roll, and the heating temperature of the roll is appropriately determined as necessary because it is related to the time of contact with the roll and the pressure of the roll. The number of rolls may be two or more, but the contact time with the heating roll can be increased by using three or more rolls. Usually, the heating temperature of the roll is higher by 30 ° C., preferably 50 ° C. or higher than the foaming start temperature of the foamable microcapsules. The thermal pressure increases as the pressure of the roll increases. However, if the pressure is too high, the foaming ratio of the laminate (3) or the laminate (6) decreases, so it is preferable to adjust the pressure while confirming the degree. Moreover, when an emboss pattern is imparted to the roll surface, a clear emboss pattern can be imparted to the surface of the laminate after foaming, and the design can be improved.

In the present invention, the outer shell of the foamable microcapsule is preferably an acrylic resin. Expandable microcapsules are low-boiling hydrocarbons that are microencapsulated with a shell wall of a copolymer such as vinylidene chloride or acrylonitrile, and are generally thermally expandable spheres having a particle size of about 10 μm to less than 30 μm. Say. By heating this to vaporize the low boiling point hydrocarbons in the microcapsules, thermal expansion occurs instantaneously. There is also a method in which hollow spheres are added simply to reduce the density. For example, around a shirasu balloon or foaming microcapsule after foaming, or around a microbubble generated in a liquid, a hollow small sphere having a thickness of several hundred nm to several μm is created by a polymerization reaction on the surface, etc. A method for embedding these has been proposed, but in the method proposed here, since the density of hollow spheres is extremely low, it is difficult to disperse in the slurry, and everything floats on the surface. Because of the situation, there was a drawback that it was extremely difficult to produce. In the present invention, unfoamed expandable microcapsules are inserted into a paper layer and formed into a sheet and then foamed. Therefore, the above problems are few. Low-boiling hydrocarbons include ethane, ethylene, propane, propene, n-butane, isobutane, butene, isobutene, n-pentane, isopentane, neopentane, n-hexane, heptane, petroleum ether and other low molecular weight hydrocarbon compounds, CCl Examples include chlorofluorocarbon compounds such as ₃ F, CCl ₂ F ₂ , CClF ₃ , and CClF ₂ —CClF ₂ , and tetraalkylsilane compounds such as tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, and trimethyl-N-propylsilane. . Among these, isobutane, n-butane, n-pentane, isopentane, n-hexane, petroleum ether and the like are preferably used. The temperature (boiling point) at which the liquefied gas vaporizes is related to the molecular weight, and the lower the molecular weight type, the lower the boiling point tends to be. Moreover, the tendency to foam at low temperature is seen, so that a boiling point is low. The capsule shell when these liquefied hydrocarbons are microencapsulated must not diverge from the inside until each liquefied hydrocarbon is thermally expanded. In the case of liquefied propane or liquefied butane, vinylidene chloride with excellent gas barrier properties is used as the outer shell of the microcapsule. However, since the outer shell of the microcapsule contains chlorine, it generates toxic gas. It is not preferable to use in an environment where people live. For this reason, the outer shell of the foamable microcapsule in the present invention is preferably an acrylic resin. In the present invention, the heat foaming start temperature is preferably 120 ° C. or higher. More preferably, it is 130 degreeC or more. When foamable microcapsules having a relatively high heating foaming start temperature of this level are used, liquefied hydrocarbons contained in the microcapsules can have high boiling points such as heptane, and thus have a relatively large molecular weight. As a result, even if the outer shell of the microcapsule is an acrylic resin, the gas barrier property is sufficiently maintained.

  In this invention, it is preferable that content of the foamable microcapsule in a sheet-like object (1) is 5 to 40 mass parts. More preferably, it is 15 to 30 mass parts. When the content of the foamable microcapsule exceeds 40 parts by mass, the density is unnecessarily lowered and the strength between the paper layers is also lowered, which is not preferable. Further, if the content of the foamable microcapsule is less than 5 parts by mass, the effect of reducing the density due to foaming is lowered, which is not preferable.

  In order to include foamable microcapsules in the sheet-like material (1), foamable microcapsules are prepared when slurry is prepared by adding various kinds of chemicals and fillers to those prepared by disaggregating and beating papermaking fibers. It can be prepared by adding and mixing capsules.

[Example 1]
50 parts by weight of softwood bleached kraft pulp (NBKP) and 50 parts by weight of hardwood bleached kraft pulp (LBKP) were disaggregated and mixed, and the beating degree was 500 ml C.I. S. F. It prepared so that it might become. 30 parts by mass of foamable microcapsules (trade name “Matsumoto Microsphere F-80”, manufactured by Matsumoto Yushi Co., Ltd.) with a foaming start temperature of 140 ° C., a wet paper strength enhancer (trade name “WS-4024”) , Manufactured by Seiko PMC Co., Ltd.), and an appropriate amount of a sulfuric acid band was added and fixed to obtain a slurry of sheet-like material (1). Similarly, a slurry of the sheet-like product (2) was prepared in the same manner as above except that the foamable microcapsules were removed. Using a circular net three-layer paper machine, the sheet-like material (1) is 140 g / m ² in the center layer by a standard method, and the sheet-like material (2) is 30 g / m ² on one side on both sides. A sheet-like material (3) having a basis weight of 200 g / m ² was prepared. At this time, the foamable microcapsules did not foam during the paper making process.

[Example 2]
A sheet-like material (3) having a basis weight of 200 g / m ² was prepared in the same manner as in Example 1 except that the foamable microcapsules of the sheet-like material (1) were changed to 15 parts by mass.

[Example 3]
A sheet-like material (3) having a basis weight of 300 g / m ² was prepared in the same manner as in Example 1 except that the basis weight of the sheet-like material (2) was changed to 80 g / m ² .

[Example 4]
Except that 10 parts by mass of vinylon binder fiber (trade name “Unitika Vinylon SML”, manufactured by Unitika Ltd.) was mixed with the slurry of (1) of the sheet-like material of Example 1, the basis weight was the same as Example 1. A sheet (3) having an amount of 200 g / m ² was prepared.

[Example 5]
Into the sheet-like material (3) obtained in Example 1, SBR latex (trade name “Smartex PA-1013”, manufactured by Mitsui Chemicals, Inc.) was impregnated so that the impregnation rate was 20% by mass in terms of solid content. Impregnation was performed to prepare a sheet (3). The total basis weight was 240 g / m ² .

[Example 6]
A sheet (5) was bonded to both sides of the sheet (3) obtained in Example 1 to prepare a laminate (6). As the sheet-like material (5), a high-density polyethylene film having a thickness of 20 μm is used, and a two-part curable epoxy adhesive is applied 3 g / m ^{2 in} terms of solid content using a roll coater. Press to bond. The total basis weight was 240 g / m ² .

[Example 7]
A laminate (6) was prepared in the same manner as in Example 6 except that the sheet-like material (5) was changed to a spunbonded nonwoven fabric having a thickness of 220 μm (trade name “Marix EB0343OW”, manufactured by Unitika Ltd.). The total basis weight was 270 g / m ² .

[Example 8]
A laminate (6) was prepared in the same manner as in Example 6 except that the sheet (5) was changed to a hard aluminum foil having a thickness of 50 μm. The total basis weight was 470 g / m ² .

[Example 9]
A laminate (6) was prepared in the same manner as in Example 8, except that the sheet (3) obtained in Example 5 was used instead of the sheet (3) obtained in Example 1. did. The total basis weight was 510 g / m ² .

[Example 10]
A laminate (6) was prepared in the same manner as in Example 8, except that the sheet (3) obtained in Example 4 was used instead of the sheet (3) obtained in Example 1. did. The total basis weight was 470 g / m ² .

[Comparative Example 1]
The foamable microcapsules in the sheet (1) were used except that foamable microcapsules with a foaming start temperature of 80 ° C. (trade name “Matsumoto Microsphere F-30” manufactured by Matsumoto Yushi Co., Ltd.) were used. A sheet-like material (1) was prepared in the same manner as in Example 1, and the sheet-like material (2) was further laminated in the same manner as in Example 1 to a basis weight of 200 g / m ² during the drying step in the papermaking step. A low density composite was made by foaming.

[Comparative Example 2]
A slurry of the sheet-like material (1) was prepared in the same manner as in Example 1, and a sheet-like material (1) having a basis weight of 200 g / m ² was prepared by a conventional method using a long net paper machine.

[Comparative Example 3]
A slurry of sheet-like material (1) was prepared in the same manner as in Example 1 except that no foamable microcapsules were contained, and a sheet-like material having a basis weight of 200 g / m ² by a regular method using a long net paper machine. (1) was created. Separately, 40 parts by mass of SBR latex (trade name “Smartex SN309”, manufactured by Nippon A & L Co., Ltd.) and foaming microcapsules (trade name “Matsumoto Microsphere F-105”, manufactured by Matsumoto Yushi Co., Ltd.) as binders 15 parts by mass and a coating material prepared by mixing and dispersing 85 parts by mass of kaolin (trade name “UW-90”, Engelhard Manufacturing Co., Ltd.) as a filler and adjusting the solid concentration to 35% by mass of the previous sheet-like material (1) A sheet-like material was prepared by coating 15 g / m ² on the front and back surfaces at a solid content conversion amount. The total basis weight was 230 g / m ² .

[heating]
The sheet-like material obtained as described above is cut into a size of 25 cm square, and is sandwiched between two pieces using an iron plate having a thickness of 2 mm and a size of 25 cm square, and is placed in an oven at 150 ° C. for 2 minutes. Heated to obtain a low density composite. The iron plate was preheated in an oven at that temperature and adjusted to the same temperature as the oven.

[Measurement of basis weight, thickness, density and expansion ratio]
The basis weight in Examples and Comparative Examples of the present invention was evaluated according to JIS P 8124, and the thickness and density were evaluated according to JIS P 8118. The expansion ratio was calculated by the following formula.
Foaming ratio (%) = Thickness after heating (mm) / Thickness before heating (mm) × 100

[Measurement of delamination strength]
The delamination strength in the examples and comparative examples of the present invention was as follows. Each sample was cut to a width of 15 mm in the vertical direction, the paper layer of the sheet (1) was peeled by 15 mm, and a tensile tester (trade name “Tensilon RTF1250” , Manufactured by A & D Co., Ltd.), the tensile strength was 10 mm / min, and the peel strength when peeled at 90 degrees was measured.

The powder falling in the examples and comparative examples of the present invention was evaluated first for papermaking, secondly for the sheet before heating, and thirdly for the sheet after heating. The first was a comprehensive evaluation of the degree of contamination of paper machine blankets, canvases, various rolls, etc., and ○ was set as an acceptable level.
○: There is little powder omission and it is at a practical level.
Δ: Slightly inferior and not practical.
X: Inferior and not practical.

In the state of powder falling of the sheet-like material after the second and third heating, a black paper was placed on each sheet-like material, a 1 kg weight was placed thereon, and this weight was pulled and moved 50 cm at 10 cm / second. The degree of powder adhesion to the subsequent black paper was visually evaluated as follows, and ○ was set as an acceptable level.
○: There is little powder omission and it is at a practical level.
Δ: Slightly inferior and not practical.
X: Inferior and not practical.

The results of Examples 1 to 10 and Comparative Examples 1 to 3 are shown in Table 1.

[Table 1]

From the results shown in Table 1, the samples of the examples all heated the sheet-like material, and the foamable microcapsules contained in the sheet-like material (1) foamed, and the intended reduction in density progressed. It was confirmed that In addition, in the case of papermaking, before foaming is started, and after foaming is started, “powder falling” due to dropping off of the microcapsules is at a level where there is no problem. There was a tendency that foaming had already started in the paper drying process during fabrication. However, since Comparative Example 1 uses foamable microcapsules having a low foaming start temperature, the paper cannot be completely foamed during the paper-making drying process, and during subsequent winding operations and heating of sheet-like materials. In this case, problems such as cracks and wrinkles in the sheet-like material occurred, and it was confirmed that there was a problem in handling. In Comparative Example 1, the density after foaming is about 0.37 g / cm ³ , whereas the low-density composites of Examples 1 to 11 using foamable microcapsules having a high foaming start temperature are 0. There was a tendency for the density to decrease to 20 g / cm ³ or less. As in Comparative Example 21, foamable microcapsules with a low foaming start temperature foam during the paper drying process, and the formation of interfiber hydrogen bonds that proceed simultaneously with foaming inhibits foaming of the foamable microcapsules. It was estimated that a low-density body was difficult to obtain. On the other hand, the sheet-like materials of Examples 1 to 11 using the foamable microcapsules having a high foaming start temperature do not foam during the paper making process, and the foamable microcapsules foam uniformly by the subsequent heat treatment, so that the foaming efficiency is high. A high and lower density sheet could be formed. In Comparative Example 2, since the configuration is only a sheet-like material with the foamable microcapsules added internally, it is confirmed that the foamable microcapsules are dropped (pulverized) at the time of papermaking, before foaming is started, and after foaming is started. The quality problem was confirmed. In Comparative Example 3, the foamed microcapsules were not internally added to the sheet-like material, and the foamed microcapsules were included in the coating layer. Before and after the start of foaming, a slight powder fall from the coating layer was confirmed. Furthermore, since foamable microcapsules are blended only in the coating layer, there is a limit to reducing the density of the entire sheet-like material, and the foaming ratio was significantly lower than in the Examples. Moreover, a binder fiber is included in the sheet-like material (1) as in Examples 4 and 10, or a binder component is impregnated in the sheet-like material (3) as in Examples 5 and 9. Thus, it was confirmed that the sheet-like product (1) has a function of improving the paper delamination strength after foaming and is effective in increasing the strength of the laminate. Furthermore, a low-density composite having various characteristics could be obtained by combining various sheet-like materials in the outermost layer. For example, by combining a polyethylene film as in Example 6, moisture resistance and water resistance could be imparted. Moreover, in Example 7, the unique touch and designability could be provided by combining the spunbond nonwoven fabric. In Examples 8 to 10, when combined with an aluminum foil, it was very light despite having a metallic appearance, and properties such as moisture resistance, water resistance, and weather resistance could be imparted.

  The low-density composite in the present invention reduces the density by foaming the foamable microcapsules, so it can be handled in the same state as a normal sheet-like material before foaming starts, and it is efficient in terms of workability and logistics Even after foaming, there is little risk of falling off the foamable microcapsules, and various performances such as cushioning, heat insulation, heat retention, and design can be achieved by combining various sheet-like materials in the outermost layer. Since it can be applied, it can be used in a wide range of fields such as building materials, stationery, and various industrial materials.

It is a schematic diagram of the laminated body which combined the sheet-like material which does not contain a foamable microcapsule on both surfaces of the sheet-like material which internally added the foamable microcapsule. A laminate in which a sheet-like material having a design property and other characteristics is combined on one side of a laminate in which a sheet-like material not containing an expandable microcapsule is combined on both sides of a sheet-like material internally containing an expandable microcapsule. It is a schematic diagram. A laminate in which a sheet-like material having a design property and other characteristics is combined on both sides of a laminate in which a sheet-like material not containing a foamable microcapsule is combined on both sides of a sheet-like material internally containing an expandable microcapsule. It is a schematic diagram.

Explanation of symbols

1. 1. Sheet-like material mainly composed of paper-making fibers, including foamable microcapsules 4. Sheet-like material mainly made of paper-making fibers Sheet

Claims (9)

  Laminating a sheet-like material (2) mainly made of papermaking fibers not containing foamable microcapsules on both sides of a sheet-like material (1) mainly made of papermaking fibers containing unfoamed foamable microcapsules, A low-density composite (4), wherein the foamable microcapsules are foamed by separately heating a laminate (3) obtained by drying the laminate (3).   A sheet (5) is bonded to at least one surface of the laminate (3) to form a laminate (6), and the foamable microcapsules are foamed by heating the laminate (6). Item 8. The low-density composite (7) according to Item 1.   The low-density composite (7) according to claim 1 or 2, wherein a sheet-like material (5) is bonded to at least one surface of the low-density composite (4).   The low density composite according to claim 2 or 3, wherein the sheet (5) is at least one selected from metal foil, resin film, paper, cloth and non-woven fabric. (7).   The low density composite according to any one of claims 1 to 4, wherein the sheet (1) is internally added and / or impregnated with an adhesive.   The low density composite according to any one of claims 1 to 5, wherein a binder fiber is internally added to the sheet-like material (1).   The low density composite according to any one of claims 1 to 6, wherein an outer shell of the foamable microcapsule is an acrylic resin.   The low-density composite according to any one of claims 1 to 7, wherein a foaming start temperature of the foamable microcapsule is 120 ° C or higher.   Any of the Claims 1-8 characterized by the addition amount of the foamable microcapsule contained in a sheet-like material (1) being 5 mass parts or more and less than 40 mass parts with respect to a sheet-like material (1). The low density composite according to claim 1.

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