JPH0428665B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-expandable sheet and a method for producing the same, and more particularly, the present invention relates to a heat-expandable sheet and a method for manufacturing the same, and in particular, the present invention is composed of unfired unexpanded vermiculite, inorganic fibers, and natural organic fibers, in which fine particles of unexpanded vermiculite are contained in an inorganic fiber flock and The present invention relates to a heat-expandable sheet formed by dispersing and filling gaps between intertwined inorganic fibers and natural organic fibers, and a method for producing the same. Conventionally, heat-expandable sheets and methods for producing the same have been known as described in the following publications. According to Japanese Patent Application Laid-Open No. 50-55603, expandable mica,
Expandable sheet materials are disclosed for positioning flexible and resilient catalyst supports, including inorganic fiber materials, inorganic binders (eg, synthetic mica flakes, montmorillonite, asbestos, ball clay). According to JP-A No. 51-64483, a foaming expandable material and an inorganic binder (for example, synthetic mica, tensile vermiculite, montmorillonite, Pall clay) are combined with a filler (for example, magnesia, alumina, silica). A packing composition is disclosed that is formulated with a liquid vehicle (e.g., water, ethanol) and is used to mount a catalyst-coated substrate within a container and to protect the catalyst support from mechanical and thermal loads. It is disclosed that it absorbs shock and can be mounted with catalyst supports having irregular shapes or dimensions and has thermal stability. JP-A No. 51-69507 discloses a flexible expandable sheet material consisting of expandable mica (for example, unexpanded vermiculite), an inorganic fiber material, and an organic elastic binder (for example, various latexes). . By the way, the present applicant has disclosed a heat-resistant inorganic elastic composite material in which expandable mica is interposed in α-sepiolite with its free expansion restricted, and a method for manufacturing the same, in JP-A-57-160949, and also in JP-A-57-160949. 58−95636
The publication discloses a heat-resistant elastic sheet-like material made of α-sepiolite, unexpanded vermiculite, an organic binder, and ceramic fibers, and a method for producing the same.
Furthermore, JP-A-58-144196 discloses a method that is an improvement on the method described in JP-A-58-95636. The object of the present invention is to provide a sheet that has improved tensile strength, improved handling properties, and has an expansion coefficient equal to or higher than the sheet of the invention described in the above-mentioned publications, and a method for manufacturing the same. The above object can be achieved by providing a sheet and a method for manufacturing the same as described in the claims. That is, the present invention consists essentially of 40-80% by weight of unfired, unexpanded vermiculite, 10-50% by weight of inorganic fibers, and 2-20% by weight of natural organic fibers, the total of which is 100% by weight. In the sheet, the unfired unexpanded vermiculite is in the form of fine particles; the inorganic fibers are in the form of a flock; the natural organic fibers are entangled with the inorganic fiber flock in a defibrated state; Fine-grained unfired unexpanded vermiculite is
The present invention relates to a heat-expandable sheet filled in the inorganic fiber flock and the intertwined gaps between the inorganic fiber flock and the natural organic fiber, and the present invention also relates to a heat-expandable sheet filled with unfired unexpanded vermiculite fine particles, inorganic fiber and defibrated natural organic fibers in amounts of 40 to 80 parts by weight, 10 to 50 parts by weight, and 2 to 20 parts by weight, respectively, based on a total of 100 parts by weight; While stirring and mixing the inorganic fibers in water, a flocculant is added to produce a slurry-like liquid in which the inorganic fibers are made into a floc; on the other hand, the defibrated natural organic fibers are thrown into water and stirred. The natural organic fiber is characterized in that: producing a slurry liquid; then forming the slurry after mixing and stirring the two slurry liquids into a sheet-like material; and then drying the sheet-like material; are intertwined with the floc-like inorganic fibers in a defibrated state, and the unfired, unexpanded vermiculite fine particles are intertwined with the floc-like inorganic fibers and between the flocs of the inorganic fibers and the natural organic fibers. It is dispersed and filled into the intertwined gaps. The present invention relates to a method for manufacturing a heat-expandable sheet. Next, the present invention will be explained in detail. The heat-expandable sheet of the present invention is mainly made of unfired unexpanded vermiculite, inorganic fibers, and natural organic fibers, where the inorganic fibers are floc-like, that is, hair-like, and the natural organic fibers are defibrated. The inorganic fibers are entangled with the hair ball of the inorganic fibers. On the other hand, unfired, unexpanded vermiculite is in the form of fine particles and is dispersed and filled in the hair ball and the intertwined spaces between the hair ball and the natural organic fibers. A schematic diagram of the sheet structure of the present invention is shown in FIG. 1, in which inorganic fiber balls 1 are intertwined with natural organic fibers 2, and unfired and unexpanded vermiculite fine particles 3 are They are dispersed within the hair ball 1 and in the intertwined gaps between the hair ball 1 and the natural organic fibers 2. Note that the inorganic fiber balls are also partially in contact with each other. By the way, as shown in FIG. 2, in the conventional sheet, an inorganic and/or organic binder 4 is used.
Inorganic fibers such as ceramic fibers 5 are bonded to each other at contact points 6, and fine vermiculite particles 3 are dispersed and filled in the space formed by these bonded fibers. Such sheets have inorganic fibers bonded together by a binder, so they have flexibility and elasticity at room temperature, and sheets using inorganic binders maintain their bonding even at high temperatures. Because of this, it has flexibility and elasticity, and in the case of sheets using only organic binders, even if this binder decomposes due to heat at high temperatures, heat will not be released into the space where the inorganic fibers are entangled. Since the expanded vermiculite is present, the above-mentioned tangles do not dissociate, so the shape of the sheet is maintained and it has flexibility and elasticity. Unlike the conventional sheet described above, the sheet of the present invention does not use either an inorganic binder or an organic elastic binder. However, at room temperature, the sheet of the present invention is superior to conventional sheets not only in flexibility and elasticity due to the intertwining of inorganic fiber wool and natural organic fibers, but also in tensile strength and handling properties.
Furthermore, in the sheet of the present invention, the natural organic fibers burn or carbonize at high temperatures, but the shape of the sheet is maintained due to the moderate expansion of vermiculite, which further increases the intertwining of the inorganic fibers. . By the way, although the raw materials are the same as the sheet of the present invention, the inorganic fibers and the natural organic fibers are intertwined with each other in the defibrated state, and there is no unfinished material in the gaps between these intermingled fibers. In the case of a sheet as shown in FIG. 3, which has a structure filled with fired unexpanded vermiculite, the elasticity at room temperature is not much different from that of the sheet of the present invention, but the tensile strength is lower than that of the inorganic fibers and the sheet of the present invention. Since the point of contact with the natural organic fiber is movable due to tensile stress, the tensile strength is extremely small compared to the tensile strength of the sheet of the present invention. Furthermore, since the natural organic fibers of the sheet burn or carbonize at high temperatures, the expansion force is smaller than that of the sheet of the present invention. The sheet of the present invention has been described above in general comparison with a sheet formed by bonding with a conventional inorganic binder and/or an organic binder, and a sheet which is made of the same material but has a different structure. Next, each raw material used in the present invention will be explained. Ceramic fibers can be advantageously used as the inorganic fibers used in the present invention. Ceramic fibers are generally made into fibers by electrically melting approximately equal amounts of high-purity silica and alumina, and then blowing the resulting stream with high-pressure air or steam, and this fiber softens at 200 to 300°C. Unlike glass fiber, it does not crystallize unless the temperature reaches 850℃ or higher, and it has excellent fire resistance and can withstand high temperatures of 1000℃ or higher. However, when the above-mentioned rivulet is turned into fibers, some shots are not turned into fibers, some shots remain stuck to the tips of the fibers, and some shots break off from the tips of the fibers. The size of these shots is generally coarse if they are not made into fibers from the beginning, and many have a particle size of 150μ or more. In addition, those that remain at the tips of the fibers or that separate from them are generally fine and
Most of the shots are about 100 to 44μ, and these make up the majority of shots. Ceramic fibers produced by the above method usually contain about 50% of the shots. Many of these shots exist in a state of being incorporated into the tangle of fibers, and it is extremely difficult to separate and remove only the shot from the tangle of fibers without destroying the fibers. Because shots are mainly spherical, they do not easily entangle with materials such as ceramic fibers or vermiculite, and they do not have expansion properties, so they do not contribute to the strength, flexibility, or elasticity of the sheet at room or high temperatures. In the case of the sheet of the present invention, it is desirable to sufficiently remove it. Conventionally, in order to remove not only the large shots trapped in the tangle of ceramic fibers but also the fine shots, the fibers had to be broken and fragmented, and the shot content suitable for use in the sheet of the present invention is It has been difficult to industrially obtain large quantities of ceramic fibers with low fiber length and long fiber length. The shot removal treatment applied to the ceramic fibers used in the sheets of the present invention is a step in which the ceramic fibers are stirred in water to form a slurry of ceramic fiber flocs. Shots are loosened in a rectangular container that can generate turbulent flow, or a cylindrical container that can generate eddy flow by pumping pressurized water through the side wall, and the fibers are incorporated into the tangle without breaking them. The process consists of three steps: separating the ceramic fibers from the shot by taking out the shot and breaking the shot attached to the tip of the fiber, and then removing the separated shot and collecting the fiber at the same time. The process is carried out by distributing the ceramic fibers in a continuous process without using any transportation device such as a liquid pump that would destroy the fibers during the process. Therefore, the ceramic fiber used in the present invention has a low shot content and long fiber length, and a sheet using this has high strength and elasticity at high temperatures. Next, two examples of specific methods for obtaining ceramic fibers used in the sheet of the present invention and having a shot content of 30% or less will be explained. Commercially available ceramic fibers are poured into water and stirred to create a slurry of ceramic fiber flocs.
Next, this slurry is gradually introduced into a rectangular container equipped with stirring blades and baffles, and at the same time, water is supplied to the container and defibrated in a slow turbulent flow at a flow rate of 5 to 50 m/min. , loosen the ceramic fiber flock and separate the shot. A slurry of disentangled ceramic fibers is sequentially overflowed from the top of the container and guided onto a moving endless screen, where the shot is sieved off and the fibers are collected. The shot content used in the sheet of the present invention is 30%
Another method for obtaining ceramic fibers will be described below. Commercially available ceramic fibers are poured into water and stirred to create a slurry of ceramic fiber flocs.
Next, this slurry is gradually introduced into a cylindrical container, and at the same time pressurized water is pumped through the side wall of this container.
A vortex is generated, the ceramic fiber floc is loosened in this vortex, and the shot is separated. A slurry of disentangled ceramic fibers is sequentially flowed out from the center of the eddy stream and guided onto a moving endless screen, which sieves the shots and collects the fibers. Next, a method for measuring the shot content in the ceramic fiber used in the present invention will be explained. first,
Weigh 20g of ceramic fiber and crush it for 10 seconds in a vibrating mill. Next, after weighing the total weight of this pulverized sample, it is placed in a 5-capacity beaker, decanted repeatedly, dried, and sieved, and what remains on a standard 44μ sieve is used as shot. Shot content (%) = Shot amount of 44μ or more (g)
/100(g)×100 Next, unfired unexpanded vermiculite will be explained. Vermiculite is a particle with a flake multilayer structure.
A hydrated mineral with a mica-like structure, which is based on a talc-like 2:1 layer structure consisting of a Si-O tetrahedral layer and a Mg-O(OH) or Al-O octahedral layer, and these layers are connected through water between the layers. It is. When heated, it dehydrates, peels and expands, stretching 10 to 25 times, giving it properties such as elasticity and heat insulation. However, due to the poor bonding strength between the layers, it becomes flaky with the slightest external force, making it difficult to maintain its shape by itself. The vermiculite used in the invention is advantageously treated with a sodium organic acid. The reason for this is that the expansion rate and expansion force of unfired, unexpanded vermiculite increase in proportion to the particle size, but when manufacturing sheets, small particles with good dispersibility are used, and the sheet of the present invention This is because it is advantageous to use particles with a particle size of 0.1 to 2.8 mm. A sheet using vermiculite with such a small particle size has low expansion force and elasticity. The present inventors have found that by replacing the cations between the layers of vermiculite particles with sodium organic acid, the expansion force and elasticity increase, and furthermore, it expands from a lower temperature than vermiculite without substitution. It has been found that even if vermiculite with a small particle size is used as in the present invention, a sheet with excellent properties can be obtained if treated with sodium organic acid. The reason why the expansion power of unfired and unexpanded vermiculite is improved by immersing it in the organic acid sodium aqueous solution is that calcium ions or magnesium ions between the layers are replaced with sodium ions. This is thought to be due to the fact that water between the layers becomes difficult to escape during heating. Next, a method for treating unexpanded vermiculite used in the sheet of the present invention with organic acid sodium will be described. A predetermined amount of unexpanded vermiculite is put into an aqueous sodium acetate solution having a concentration of 1 to 3 normal, and immersed for example for 30 minutes to 5 hours, preferably 1 hour, then washed with water and dried at 100°C. Natural organic fibers suitable for use in the sheet of the present invention are chain polymers with appropriate length, molecules with appropriate flexibility, non-adhesive silk fibers, wool, etc. These are cashmere, mohair, wheat culm, coconut, Manila hemp, flax, hemp, cotton, kapoku, pulp, and cotton linters, and any one or two or more types selected from these can be used. The flocculants used in producing the sheet of the present invention include polyacrylamide, polyacrylic hydrochloric acid, polyethyleneimine, polysulfuric acid, polyamyl chloride,
One or more selected from ferric chlorides can be used, and among them, polyacrylamide flocculants, sulfuric acid, and the like can be advantageously used. Next, the reason for limiting the blending weight ratio of raw materials in the present invention will be explained. If the unfired unexpanded vermiculite is less than 40% by weight, the sheet will have less expansion power, while if it is less than 80% by weight
If the amount is higher, the tensile strength and flexibility will be lower, so the amount of unfired, unexpanded vermiculite must be within the range of 40 to 80% by weight. If the amount of inorganic fiber is less than 10% by weight, the floc of this fiber will be reduced, resulting in a decrease in tensile strength, elasticity, and bending strength;
If the amount is larger, the tensile strength and bending strength will increase, but the expansion force will decrease, so the content of the inorganic fibers must be within the range of 10 to 50% by weight. If the natural organic fiber content is less than 2% by weight, the tensile strength and bending strength will be low, while if it is more than 20% by weight, the fibers will be burnt out or carbonized when the sheet is used at high temperatures, resulting in the tensile strength and bending strength of the sheet being reduced. Because of its small size, the content of natural organic fibers should be within the range of 2 to 20% by weight. Furthermore, the present inventors have improved the elasticity of the sheet by attaching an organic polymer film to one or both sides of the sheet made of each of the above materials, or by sealing the entire surface of the sheet with an organic polymer film. It has been found that it is possible to obtain a sheet that has flexibility and strength that can be handled at room temperature without impairing its excellent properties such as expandability. The above-mentioned organic polymer film may be attached or sealed to the sheet using a known adhesive, or may be carried out by shrink packing, vacuum packing, or the like. However, as mentioned above, if the amount of organic polymer film used for pasting or sealing is too large, the elasticity and flexibility of the sheet will be adversely affected.
Therefore, the present inventors have experimentally determined that the amount of organic polymer film is proportional to the weight of the sheet to be pasted or sealed.
It was found to be less than 0.5%. Further, as the material for the organic polymer film, regenerated cellulose, cellulose derivatives, polyolefin, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyester, polyethylene, hydrochloric acid rubber, polyamide, fluororesin, etc. are advantageous. Next, the present invention will be explained with reference to examples. Example 1 Unfired unexpanded vermiculite (average particle size 2.5 mm) from South Africa was obtained by stirring in a 1N sodium acetate solution at a temperature of 80° C. for 3 hours and then drying. 210g of vermiculite obtained in this way
and 105 g of ceramic fiber with a shot content of 25% (trade name Ibiwool) were thoroughly stirred and mixed in 30 g of water. To this was added 200 ml of a 0.1% aqueous solution of a commercially available polyacrylamide flocculant, and the mixture was further stirred and mixed. Craft valve made from red pine and beaten separately
30 g was thoroughly stirred in 10 g of water to prepare a slurry-like aqueous solution. After mixing and stirring the above two types of aqueous solutions, they were formed into a 10 mm thick sheet using a square hand paper machine, pressed between stainless steel flat plates in a wet state, and then dried. A sheet of 45 cm x 20 cm x 5 mm was obtained. The bulk density of this sheet was 0.6 g/cm ² and its properties were as shown in the table. Example 2 Among the raw materials in Example 1, beaten Manila hemp was used instead of beaten kraft pulp made from red pine, and a 45 cm
A 20 cm x 5 mm sheet was obtained. This sheet bulk density is
The amount was 0.6 g/cm ³ and the properties were as shown in the table. Example 3 Among the raw materials in Example 1, unfired unexpanded vermiculite from South Africa (average particle size 2.5 mm) was replaced with unfired unexpanded vermiculite from South Africa with a particle size in the range of 1.19 to 1.41 mm. Using the same method as in Example 1, 45 cm x 20
A cm×5 mm sheet was obtained. The bulk density of this sheet is
The amount was 0.6 g/cm ³ and the properties were as shown in the table. Example 4 Among the raw materials in Example 1, beaten Manila hemp was used instead of beaten kraft pulp made from red pine, and South African unfired and unexpanded vermiculite (average particle size 2.5 mm) from South Africa was used instead. Using unburned, unexpanded vermiculite that had been sieved to have a particle size in the range of 1.19 to 1.41 mm, it was made into 45 cm x 20 cm x 5 mm by the same method as in Example 1.
I got a sheet of The bulk density of this sheet is 0.6g/
cm ³ and its properties are as shown in the table. Comparative Example 1 210 g of unfired unexpanded vermiculite from South Africa (average particle size 2.5 mm), 105 g of ceramic fiber with a shot content of 25%, and 30 g of beaten kraft pulp made from red pine were thoroughly stirred in 40 g of water. Mixed. To this was added 200 ml of a 0.1% aqueous solution of a commercially available polyacrylamide flocculant, and the mixture was further stirred and mixed. This slurry solution was formed into a 10 mm thick sheet using a square hand paper machine, and after being pressed between stainless steel flat plates in a wet state,
After drying, a sheet measuring 45 cm x 20 cm x 5 mm was obtained. The bulk density of this sheet was 0.6 g/cm ³ and its properties were as shown in the table. Comparative Example 2 210 g of unfired unexpanded vermiculite from South Africa (average particle size 2.5 mm), 105 g of ceramic fiber, and 65 ml of a 40% solution of styrene-butadiene latex.
and 130ml of a 1% solution of montmorillonite were thoroughly stirred with 40ml of water. To this was added 100 ml of a 10% solution of sulfuric acid band, and the mixture was further stirred and mixed. This slurry solution was formed into a 10 mm thick sheet using a square hand paper machine, which was pressed between stainless steel plates in a wet state, and then dried into a 45 cm x 20 mm sheet.
A sheet of cm x 5 mm was obtained. The bulk density of this sheet is
It was 0.6 g/cm ³ and its properties were as shown in the table.

【table】

[Table] As is clear from the table above, the sheets obtained in Examples 1 to 4 of the present invention have approximately twice the normal temperature tensile strength and recovery rate compared to the sheets of Comparative Examples, especially Comparative Example 2. It can be seen that the expansion coefficient is improved by 30 to 40% compared to Comparative Example 1. As described above, the present invention provides a sheet that has improved tensile strength compared to conventional sheets, has good handling properties, and has an expansion coefficient that is equal to or higher than that of conventional sheets, and a method for manufacturing the same. can do.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the structure of the sheet of the present invention, FIG. 2 is a schematic diagram showing the structure of the sheet of Comparative Example 2, and FIG. 3 is a schematic diagram showing the structure of the sheet of Comparative Example 1. . 1...Inorganic fiber flock, 2...Natural organic fiber, 3...Vermiculite fine particles, 4...Binder, 5
...Inorganic fiber, 6...Contact point between inorganic fibers.

Claims (1)

[Claims] 1. 40 to 80% by weight of unfired, unexpanded vermiculite
and 10-50% by weight of inorganic fibers and 2-2% of natural organic fibers.
20% by weight, and the sum of these is
100% by weight of the sheet, wherein: the unfired unexpanded vermiculite is in the form of fine particles; the inorganic fiber is in the form of a floc; the natural organic fiber is entangled with the inorganic fiber floc in a defibrated state; A heat-expandable sheet comprising: the fine-grained unfired unexpanded vermiculite dispersed and filled in the inorganic fiber flock and the intertwined gaps between the inorganic fiber flock and the natural organic fiber; 2. The unfired unexpanded vermiculite is unexpanded vermiculite obtained by immersing it in an organic acid sodium aqueous solution and replacing cations other than sodium ions between the layers of the unexpanded vermiculite with sodium. Sheet described in item 1. 3. The sheet according to claim 2, wherein the organic acid aqueous solution is a sodium acetate aqueous solution. 4 The particle size of the unfired unexpanded vermiculite is
Claim 1 within the range of 0.1 to 2.83 mm
Sheet with section description. 5. The sheet according to claim 1, wherein the inorganic fibers are mainly composed of silica and alumina, and have a crystallization temperature of 850°C or higher. 6. Claim 1, wherein the inorganic fiber has a shot content of 30% or less.
Or the sheet described in item 5. 7. The natural organic fiber is a chain polymer, has flexibility and non-adhesion, and is suitable for silk, wool,
The sheet according to claim 1, which is made of one or more types selected from cashmere, mohair, wheat culm, coconut, Manila hemp, flax, hemp, kapoku, pulp, and cotton linters. 8 The compressibility of the sheet is 30% or more and the recovery is 70% when measured using a 2 inch square anvil under a load of 12.5 kg in accordance with ASTM F-36-79 test method.
% or more, the sheet according to claim 1. 9. 40 to 80 parts by weight of each of unfired unexpanded vermiculite fine particles, inorganic fibers, and defibrated natural organic fibers per 100 parts by weight of the total,
10 to 50 parts by weight and 2 to 20 parts by weight are prepared; a slurry in which the unfired unexpanded vermiculite and inorganic fibers are stirred and mixed in water and a flocculant is added to form the inorganic fibers into a floc. On the other hand, the defibrated natural organic fibers are stirred in water to produce a slurry liquid; Next, the two types of slurry liquids are mixed and stirred, and the slurry is then formed into a sheet-like material. paper-forming; and then drying the sheet-like material; characterized in that the natural organic fibers are entangled with floc-like inorganic fibers in a defibrated state, and the unfired unexpanded vermiculite fine particles is dispersed and filled in the flock of the inorganic fibers and in the intertwined spaces between the flock of inorganic fibers and the natural organic fibers.