JP6461657B2 - Method for producing inorganic foam - Google Patents

Description

  The present invention relates to a method for producing an inorganic foam, and more particularly to a method for producing an inorganic foam having heat insulation, nonflammability, light weight and sufficient mechanical strength.

A foam obtained by foaming a synthetic resin is lightweight and excellent in heat insulating properties, and is widely used in heat insulating materials for various devices and buildings. In particular, among such foams, vinyl chloride resin foams are excellent in terms of chemical resistance, mechanical strength, etc., and are widely used.
However, although this vinyl chloride resin is flame-retardant, it is not nonflammable. In addition, it is relatively weak against heat and has a drawback of large volume shrinkage in a high temperature atmosphere.

Therefore, in order to improve this point, an inorganic foam (hereinafter, also simply referred to as a foam) obtained by mixing and foaming an inorganic substance that has excellent heat resistance and can suppress volume shrinkage even when heated is reduced. Has been developed.
For example, an inorganic substance filler such as calcium carbonate or talc is used as a base material, and after adding a vinyl chloride resin, a foaming agent and an organic solvent, the mixture is kneaded with a kneader, and the obtained kneaded product is placed in a pressurized mold. A foamed product is known that is heated and cooled and then decompressed. According to this method, it is possible to obtain a foam containing an inorganic substance filler in a high ratio.
However, such a foam has a small total calorific value and a maximum heat generation rate at the time of combustion. However, the shrinkage and cracks generated in a high-temperature atmosphere are remarkable, and the non-combustibility shown in Article 2-9 of the Building Standard Law. It did not pass the exothermicity test by the cone calorimeter which is a performance evaluation test as a material and a semi-incombustible material.

  On the other hand, metal hydroxides such as aluminum hydroxide are known as flame retardants for synthetic resins, and flame retardancy can be imparted by blending metal hydroxides into synthetic resin foams to form inorganic foams. It has been known. However, when a large amount of metal hydroxide is blended in the inorganic foam, the foamability is lowered, and it is difficult to obtain a foam having a low apparent density. Further, there is a problem that the degree of shrinkage and cracking of the foam is increased due to the dehydration reaction of aluminum hydroxide during combustion. Such a thing does not pass the performance evaluation test in the said exothermic test.

  In order to solve these problems, the present applicant has proposed a method for producing an inorganic foam in which 10 to 30 parts by weight of metal hydroxide is blended and a predetermined amount of inorganic fiber whiskers are added (Patent Document 1). .

  By this production method, it has become possible to obtain an inorganic foam having improved nonflammability, which has a small total heat generation amount during combustion and a maximum heat generation rate, and which can suppress shrinkage and surface cracking.

JP2007-39644

  However, compared with the inorganic foam obtained by the method described in Patent Document 1, a foam having further superior nonflammability is desired. Specifically, an inorganic foam that exhibits non-flammability more stably even when a fire actually occurs is desired. For that purpose, a method of further increasing the blending amount of the metal hydroxide in the inorganic foam can be considered. However, if the blending amount of the metal hydroxide is increased too much, specifically, if the blending amount of aluminum hydroxide exceeds 30 parts by weight on the premise of blending of Patent Document 1, it is foamed to a desired low apparent density. In addition, there was a problem that the obtained foam was remarkably contracted during a combustion test and a crack was generated.

  INDUSTRIAL APPLICABILITY The present invention provides an inorganic system that can stably obtain a foam having a low apparent density even when a large amount of metal hydroxide is blended, and can stably obtain a foam that exhibits nonflammability. It aims at providing the manufacturing method of a foam.

According to this invention, the manufacturing method of the inorganic foam shown below is provided.
[1] (a) 5-25 parts by weight of vinyl chloride resin, (b) 30-50 parts by weight of aluminum hydroxide, (c) 20 parts by weight or more of calcium hydroxide, (d) 6-15 parts by weight of calcium sulfate whiskers, (E) 0.5 to 3 parts by weight of diantimony trioxide, and (f) 0 to 15 parts by weight of other inorganic fillers (however, the sum of (a) to (f) is 100 parts by weight). Manufacturing an inorganic foam, kneading a pyrolytic foaming agent and an aromatic hydrocarbon solvent, and heating and cooling the kneaded product in a pressurized mold and then depressurizing the foam. Method.

  According to the method for producing an inorganic foam of the present invention, a large amount of metal hydroxide is blended by using aluminum hydroxide and calcium hydroxide together as metal hydroxide and using calcium sulfate whisker as inorganic fiber whisker. Even if the amount of the metal hydroxide is increased by adding a specific amount of calcium sulfate whisker, a foam having a low apparent density can be stably obtained. Volume shrinkage and generation of cracks are prevented and suppressed, and an inorganic foam having excellent nonflammability and low apparent density can be obtained.

Hereafter, the manufacturing method of the inorganic type foam of this invention is demonstrated in detail.
In the production method of the present invention, (a) vinyl chloride resin, (b) aluminum hydroxide, (c) calcium hydroxide, (d) calcium sulfate whisker, (e) antimony trioxide, and (f) other An inorganic material is obtained by kneading an inorganic filler, a pyrolytic foaming agent, and an aromatic hydrocarbon solvent, heating and cooling the kneaded material in a pressurized mold, and then depressurizing and foaming. A foam is produced.

  The vinyl chloride resin (a) used in the present invention may be a polymer containing 50% by weight or more of vinyl chloride as a main component, and general vinyl chloride resins can be widely used. Moreover, the property is not particularly limited, and any of a paste resin by an emulsion polymerization method, a suspension resin by a suspension polymerization method, and a bulk polymerization resin by a bulk polymerization method can be used. However, a paste resin having a small particle size is preferable for the production of a foam.

  The vinyl chloride resin preferably has an average degree of polymerization of 1000 to 5000, and more preferably has an average degree of polymerization of 2000 to 4000. When the average degree of polymerization is within this range, a foam having a low apparent density can be obtained more stably. These vinyl chloride resins are not limited to the use of a single resin, and two or more kinds of resins having different polymerization degrees can be mixed and used.

  The average degree of polymerization of the vinyl chloride resin is measured based on JIS K 6720-2 (1999). Specifically, about 0.2 g of vinyl chloride resin dried at room temperature was weighed into a 50 ml volumetric flask, and about 40 ml of nitrobenzene was added thereto and heated to 100 ° C. After confirming that the sample was completely dissolved, the volumetric flask was cooled, and nitrobenzene was newly added to adjust the temperature to 30 ° C. to a total volume of 50 ml. This solution was used as a test solution, and an automatic viscometer (Ubbelohde viscometer) was obtained. ), While measuring the falling seconds of the test solution, measure the falling seconds of nitrobenzene by the same method, and determine the specific viscosity according to the same JIS. The specific viscosity is measured three times and the average value is obtained. Subsequently, using the average value of the specific viscosity, the average degree of polymerization of the vinyl chloride resin is calculated from the formulas (1) and (2) described in the same JIS.

  The amount of the vinyl chloride resin is 5 to 25 parts by weight, where the total of the above (a) to (f) is 100 parts by weight. If the blending amount is too small, it may be impossible to produce an inorganic foam. On the other hand, if the amount is too large, the incombustibility may be reduced. From this viewpoint, the lower limit of the amount is preferably 10 parts by weight, more preferably 15 parts by weight. Moreover, it is preferable that the upper limit of this compounding quantity is 23 weight part, More preferably, it is 20 weight part.

In the present invention, (b) aluminum hydroxide and (c) calcium hydroxide are used as the metal hydroxide for imparting incombustibility.
Aluminum hydroxide and calcium hydroxide are preferred because the dehydration temperature is not so low as to start dehydration at the time of foam production, and is not so high as to start dehydration after the combustion of the foam has considerably progressed. That is, aluminum hydroxide and calcium hydroxide are dehydrated and decomposed when the foam is heated to 200 to 400 ° C., and the heat generated at that time reduces the amount of heat generated during the combustion of the foam to increase the temperature of the foam. Can be suppressed.

  In general, the smaller the particle size of aluminum hydroxide and calcium hydroxide, the greater the effect on combustion characteristics. 100 mesh pass is preferable, 200 mesh pass is more preferable, and 300 mesh pass is particularly preferable. If the particle size is too large, the shrinkage of the specimen during combustion becomes large, and it becomes difficult to satisfy the criteria of the exothermic test by a cone calorimeter, which is a performance evaluation test as a non-combustible material.

  In addition, the said mesh means the number of eyes per inch in a sieve.

  (B) The compounding quantity of aluminum hydroxide is 30-50 weight part by making the sum total of said (a)-(f) into 100 weight part. With aluminum hydroxide alone, when it exceeds 30 parts by weight, it becomes difficult to obtain a low-density foam. On the other hand, when combined with calcium hydroxide, even if the blending amount is 30 parts by weight or more, 50 parts by weight. A foam with a low apparent density can be obtained as long as it is below. From the viewpoint of improving nonflammability, the lower limit of the amount is preferably 35 parts by weight or more. On the other hand, the upper limit of the blending amount is preferably 45 parts by weight for ease of foam production.

  (C) The compounding quantity of calcium hydroxide is 20 weight part or more by making the sum total of said (a)-(f) into 100 weight part. If the amount is too small, the effect of increasing the amount of (b) aluminum hydroxide may be reduced. On the other hand, the upper limit is preferably 40 parts by weight, more preferably 30 parts by weight. When calcium hydroxide is combined with aluminum hydroxide, the amount of aluminum hydroxide is increased, and more than 20 parts by weight of calcium hydroxide can be blended, so that the total amount of metal hydroxide is 50 parts by weight. It can mix | blend above.

  In the present invention, (d) calcium sulfate whisker is blended as the inorganic fiber whisker. Since inorganic fiber whiskers are uniformly dispersed in the foam, a three-dimensional network structure of inorganic fiber whiskers is formed in the foam, and the shape of the foam is maintained even during combustion to prevent surface cracking. be able to. Among inorganic fiber whiskers, calcium sulfate whiskers are excellent in preventing shrinkage during combustion and in suppressing cracking, and even if the blending amount of (b) aluminum hydroxide or (c) calcium hydroxide is increased, An inorganic foam having a low apparent density that cannot be obtained with other inorganic fiber whiskers such as magnesium sulfate whiskers can be obtained.

  The amount of calcium sulfate whisker is 6 to 15 parts by weight, preferably 7 to 14 parts by weight, with the total of (a) to (f) as 100 parts by weight. If the amount is too small, the desired shrinkage prevention effect, crack suppression effect, and low apparent density reduction effect may not be obtained. On the other hand, if the amount is too large, a foam having a low apparent density may not be obtained, or the closed cell ratio may be reduced.

  In the present invention, the average fiber diameter of the calcium sulfate whisker is preferably 5 μm or less, and more preferably 3 μm or less. The lower limit of the average fiber diameter is usually 0.1 μm. When the fiber diameter is 5 μm or less, the primary particle aspect ratio increases, so the effect of maintaining the foam shape due to the three-dimensional entanglement of the inorganic fiber whiskers increases. It is possible to effectively prevent the occurrence of cracks on the surface.

The average fiber length of the calcium sulfate whisker is preferably 200 μm or less, and more preferably 100 μm or less. The lower limit of the average fiber length is usually 1 μm. When the average fiber length is 200 μm or less, the obtained foam can have a high closed cell ratio and can prevent high density due to shrinkage and achieve high foaming efficiency commensurate with the amount of chemical foaming agent. .
The “average fiber length” refers to the arithmetic average value of the measured values of the fiber lengths of 50 whiskers based on a 1000 × electron micrograph. The “average fiber diameter” refers to the arithmetic average value of the fiber diameters of 100 inorganic fiber whiskers. The fiber diameter refers to the diameter when the fiber cross-sectional shape is circular, and when the fiber cross-sectional shape is non-circular, the diameter of a circle having the same area as the cross-sectional area is referred to as the fiber diameter. I reckon.

  In the present invention, (e) diantimony trioxide is used as a flame retardant. Antimony trioxide forms a strong carbonized film on the surface of the foam during combustion, and exhibits the effect of suppressing ignition of the foam and continuation of combustion.

  The blending amount of diantimony trioxide is 0.5 to 3 parts by weight with 100 parts by weight of the sum of (a) to (f). If the amount is too large, volume shrinkage is likely to occur due to the weight loss of the flame retardant itself during foam combustion. At the same time, it becomes difficult to produce a foam having a low apparent density. On the other hand, if the blending amount is too small, the effect of suppressing ignition during combustion and continuation of combustion may not be exhibited.

  In the present invention, (f) other inorganic filler different from the inorganic compound is blended. Examples of the inorganic filler include carbonates such as titanium, iron, and zinc, sulfates, silicates, phosphates, borates, oxides, or powders of these hydrates. , Calcium carbonate, magnesium carbonate, zinc oxide, gypsum, barium sulfate, aluminum silicate, magnesium silicate, calcium silicate, aluminum sulfate, magnesium sulfate, calcium sulfate, magnesium phosphate, glass flakes, hydrated aluminum, hydrated gypsum , Silica, talc, clay, bentonite and the like. Moreover, you may mix | blend other metal hydroxides other than aluminum hydroxide and calcium hydroxide, such as magnesium hydroxide, as an inorganic filler.

  The blending amount of the inorganic filler is 0 to 15 parts by weight (provided that 0 part by weight is included), where the total of the above (a) to (f) is 100 parts by weight.

  As the pyrolytic foaming agent used in the present invention, a so-called chemical foaming agent is used, and organic foaming agents such as azodicarbonamide, azobisisobutyronitrile, dinitrosopentamethylenetetramine, and p-toluenesulfonyl human salt. Examples include inorganic foaming agents such as sodium bicarbonate and ammonium chloride, such as zido and p, p'-oxybis (benzenesulfonylhydrazide). These foaming agents can be used alone or in combination of two or more. The foaming agent to be used is selected from those described above and is not particularly limited. However, azodicarbonamide and azobisisobutyronitrile are preferably used because a desired apparent density is easily obtained. The pyrolytic foaming agent may be used in combination with a urea-based foaming aid, if necessary.

  The blending amount of the pyrolytic foaming agent varies depending on the desired apparent density, the type of foaming agent used, the type of organic solvent and the amount thereof, but usually 5 parts per 100 parts by weight of the vinyl chloride resin. -100 parts by weight, preferably 10-50 parts by weight, particularly preferably 20-50 parts by weight. If the blending amount of the pyrolytic foaming agent is too small, only a product having a large apparent density can be obtained. If the blending amount of the foaming agent is too large, the cell membrane may be destroyed at the time of foaming, resulting in open cells and lowering the closed cell ratio. There is.

  As the aromatic hydrocarbon solvent used in the present invention, those generally used for the production of this kind of inorganic foam can be widely used. Examples of the aromatic hydrocarbon include toluene, xylene and the like. These solvents can be used alone or in admixture of two or more. The blending amount of the aromatic hydrocarbon is 30 to 100 parts by weight, preferably 40 to 80 parts by weight, with the total of (a) to (f) as 100 parts by weight.

  Other stabilizers such as dibasic phosphite, dibasic lead stearate, tribasic lead sulfate, zinc stearate, calcium stearate and titanium oxide for the purpose of preventing degradation of vinyl chloride resin A pigment such as an antistatic agent such as an alkyl sulfonate can be appropriately used as necessary.

Next, an example of the manufacturing method of the inorganic foam of this invention is demonstrated.
First, in the kneader, the vinyl chloride resin, aluminum hydroxide, calcium hydroxide, calcium sulfate whisker, antimony trioxide, and other inorganic fillers, pyrolytic foaming agent, and addition of stabilizers as necessary The agent is mixed in the above-described ratio, and kneaded while adding the required amount of the aromatic hydrocarbon solvent in several portions. At this time, the temperature of the kneaded material in the kneader is preferably in the range of 0 to 60 ° C. so that gelation of the vinyl chloride resin and decomposition of the foaming agent do not occur and efficient kneading proceeds. .

Next, the obtained kneaded material is filled in the mold without any gap, and is pressurized and sealed with a hydraulically driven hot press. The press pressure at this time is selected to be 130 kgf / cm ² or more. Next, the mold is heated to 100 to 170 ° C. under a press and held in that state for 5 to 40 minutes to promote gelation of the vinyl chloride resin and decomposition of the foaming agent.
As a result, the vinyl chloride resin is dissolved in the solvent, and the fine particles such as the inorganic fiber whisker, the metal hydroxide, and the inorganic filler are surrounded by the vinyl chloride resin. At the same time, because the inside of the mold is in a high temperature and high pressure state, the decomposition gas of the foaming agent is uniformly diffused into the gelatinized vinyl chloride resin and inorganic fiber whiskers, metal hydroxides, inorganic fillers, etc. It becomes a state.

After the reaction is sufficiently performed, the mold is cooled to 0 to 80 ° C. using a cooling medium such as water, and then the pressure of the press is released to remove the product from the mold.
At this point, the product becomes a foam of 1.43-1.67 times the desired apparent density (60-70% of the desired expansion ratio) (primary foaming).
Next, the product is heated again to 90 to 120 ° C. in a warm air circulating apparatus such as an oven under normal pressure, and expanded to a target apparent density (secondary foaming).
After inflating to the target apparent density, the temperature is lowered again to room temperature and curing is performed to stabilize the shape.
Then, if a product is heated gradually and an organic solvent is volatilized and removed, an inorganic type foam will be obtained.

The inorganic foam obtained by the production method according to the present invention is formed by closed cells having a cell wall mainly composed of a metal hydroxide such as aluminum hydroxide. It has sound absorption and also has mechanical strength, dimensional stability, and nonflammability. Further, in the inorganic foam obtained by the production method according to the present invention, a predetermined amount of inorganic fiber whiskers are added and dispersed, so that a three-dimensional network structure of calcium sulfate whiskers is formed in the foam. Even during combustion, the shape of the foam is maintained, and the foam is capable of preventing the occurrence of cracks on the surface.
In addition, the inorganic foam obtained by the production method according to the present invention using aluminum hydroxide and calcium hydroxide is such that when the foam is heated to 200 to 400 ° C., the metal hydroxide is dehydrated and decomposed. In addition, the heat absorption at that time makes it possible to reduce the amount of heat generated during the combustion of the foam, to suppress the temperature rise of the foam, and to further improve the nonflammability.

In addition, the inorganic foam of the present invention contains diantimony trioxide, and a strong carbonized film is formed on the foam surface at the time of combustion, so the effect of suppressing the ignition of the foam and the continuation of combustion is exhibited. It has excellent flame retardancy. In order to the flame retardancy made higher, the apparent density of the foam is preferably from ^{40kg / m 3 ~100kg / m 3} , also the content of foam 1 cm ³ per vinyl chloride resin 0 It is preferable to blend the vinyl chloride resin so as not to exceed 0.05 g. Moreover, it is preferable that the thickness of a foam is at least 10 mm or more, More preferably, it is 20 mm or more, More preferably, it is 30 mm or more. On the other hand, the upper limit of the thickness is approximately 100 mm, preferably 80 mm, more preferably 60 mm, and still more preferably 50 mm.

The inorganic foam obtained by the production method according to the present invention passes the exothermic test by a cone calorimeter, which is a performance evaluation test as a non-combustible material shown in Building Standard Act Article 2 No. 9. Of course, it is suitable for use as an insulation material for buildings, as well as for earthquake-resistant slit materials, firestop materials, building materials such as walls, floors, roofs and ducts of buildings, interior materials for vehicles, and components of various devices. It is something that can be done.

The raw materials used in the examples and comparative examples are shown below.
[material]
(1) Vinyl chloride resin:
Vinyl chloride resin (manufactured by Kaneka Corporation, product name: PSL-31, polymerization degree: 1600)
(2) Metal hydroxide:
Aluminum hydroxide (350 mesh pass)
Calcium hydroxide (400 mesh pass)
(3) Inorganic fiber whisker:
Calcium sulfate whisker (manufactured by Toshin Kasei Co., Ltd., average fiber diameter: 1 μm, average fiber length: 50 μm)
Magnesium sulfate whisker (manufactured by Ube Materials Co., Ltd., product name: Moss Heidi, average fiber diameter: 0.5 μm, average fiber length: 20 μm)
(4) Antimony trioxide (Suzuhiro Chemical Co., Ltd., product name: AT3)
(5) Inorganic filler:
Calcium silicate (400 mesh pass)
(6) Pyrolytic foaming agent:
Azobisisobutyronitrile (Otsuka Chemical Co., Ltd., product name: AIBN)
(7) Aromatic hydrocarbon solvent Toluene

Examples 1 to 3, Comparative Examples 1 and 2
First, the aforementioned raw materials were blended so as to have the blending amounts shown in Table 1, and kneaded to obtain a kneaded product.
For kneading, all raw materials except for toluene are put into a kneader, kneaded for 15 minutes, then toluene is added in four portions, and kneaded for 15 minutes every time one portion of toluene is added, for a total of 60 minutes. It was. Further, during kneading, the temperature of the kneaded product was adjusted to 50 ° C.
Next, the obtained kneaded material was filled in a 120 mm × 120 mm, 25 mm deep mold without any gap, and the upper part was capped and pressurized with a pressure press at a pressure of 150 kgf / cm ² . Thereafter, the mold is heated to 150 ° C. and held for 20 minutes to gel the vinyl chloride resin in the kneaded product and decompose the foaming agent, then immediately cooled to 50 ° C. and held for 30 minutes, It was opened to obtain a plate-like inorganic foam.
Subsequently, the obtained foam was subjected to secondary foaming by storing in an oven at 80 ° C. for 2 hours. Then, after leaving it to stand in a room at 20 ° C. for 12 hours and cooling (curing), it was left again in an oven at 80 ° C. for 24 hours to volatilize the remaining toluene. Then, after standing for 12 hours in a room at 20 ° C. and cooling (curing), the physical properties of the foam were measured. The measurement results are shown in Table 1.

  In Examples 1 to 3, an inorganic foam having a low apparent density could be obtained even when the compounding amount of the metal hydroxide was increased as compared with the conventional one. The obtained foam was free from shrinkage and cracking, had excellent nonflammability, and had a small total calorific value.

Comparative Example 1
(D) In this example, magnesium sulfate whiskers are used instead of calcium sulfate whiskers. When the blending amounts of aluminum hydroxide and calcium hydroxide were the same as in the examples, the foamability was lowered, and a foam having a low apparent density could not be obtained. Moreover, since the obtained foam had high apparent density in the combustion test, it ignited and the total calorific value was high.

Comparative Example 2
(D) It is the example which reduced the compounding quantity of the calcium sulfate whisker. Although foamability was improved and a foam with a low apparent density was obtained, the amount of calcium sulfate whiskers was too small, resulting in large shrinkage and ignition during the combustion test, resulting in a high total calorific value. .

Various physical properties in the table were measured and evaluated as follows.
* Thermal conductivity Thermal conductivity is measured by cutting out a test piece from a foam into a length of 200 mm × width of 200 mm × thickness of 30 mm, and using the plate heat flow meter method described in JIS A 1412-2 (1999) (two heat flow meters). System, high temperature side 38 ° C., low temperature side 8 ° C., average temperature 23 ° C.).

* Apparent Density A test piece was cut out from the foam into a length of 200 mm × width of 200 mm × thickness of 30 mm, and its volume and weight were measured and calculated.

* Total calorific value and maximum heat generation rate Exothermic tests were conducted using a corn calorimeter (Toyo Seiki Co., Ltd. corn calorimeter C3) in accordance with ISO 5660 part 1, and 10 minutes and 20 minutes after the start of ignition. The total calorific value and each maximum exotherm rate were measured.
In addition, the test body in this test used what was cut out from the foam to a size of 99 mm × 99 mm × 30 mm square, cured in an oven at 80 ° C. for 3 days, and then allowed to stand at 23 ° C. for 24 hours or more. .
The standards for incombustibility in the corn calorimeter are as follows (the quasi-incombustibility standards in parentheses).
(1) The total calorific value for 20 minutes (10 minutes) after the start of heating is 8 MJ / m ² or less.
(2) The maximum heat generation rate should not exceed 200 kW / m ² for 20 minutes (10 minutes) after the start of heating for 10 seconds or more.
(3) There should be no cracks or holes reaching the back side, which is harmful to fire prevention, for 20 minutes (10 minutes) after the start of heating.

* Volume shrinkage In the exothermicity test using the cone calorimeter, the test specimen is wrapped with aluminum foil on the side and the back and placed in a holding frame, and the back side is filled with inorganic fibers before the specimen holder. Pushed into. The holding frame covered a part of the end of the upper surface of the test piece (the surface facing the upper side of the 99 mm × 99 mm surface (radiation heat exposure surface)) with the frame. Specifically, the frame body was covered from each side of a 99 mm square that forms the upper surface of the test body to a location that entered 2.5 mm inside. As a result, in the test, a 94 mm square portion of the upper surface of the test body became a radiant heat exposed portion. The shrinkage referred to here is the frame body after the exothermic test by the corn calorimeter (10 minutes after the start of heating for quasi-incombustibility evaluation and 20 minutes after the start of heating for evaluation of nonflammability) with the frame installed. The test specimens were observed from directly above at the respective positions around the entire circumference of the specimen and evaluated according to the following criteria.
○: Aluminum foil located on the back of the specimen is not recognized.
X: As a result of contraction of the test body, a gap is generated between the frame body and the test body, and an aluminum foil located on the back surface of the test body is observed through the gap.

* Generation of cracks After the exothermic test by the cone calorimeter (10 minutes after the start of heating for quasi-incombustible evaluation, 20 minutes after the start of heating for non-flammable evaluation), the specimen was evaluated according to the following criteria. did.
○: No crack or hole reaching from the front surface to the back surface of the specimen.
X: Cracks or holes reaching from the front surface to the back surface of the specimen are observed.

* Ignition status Ignition status was evaluated according to the following criteria.
○: Ignition was observed on the specimen during the exothermic test.
X: Ignition was not observed on the specimen during the exothermic test.
Although not related to the standard of nonflammability, the total calorific value and the maximum instantaneous heating rate tended to increase when the specimen was ignited during the exothermic test.

Claims (1)

  (A) 5 to 25 parts by weight of vinyl chloride resin, (b) 30 to 50 parts by weight of aluminum hydroxide, (c) 20 parts by weight or more of calcium hydroxide, (d) 6 to 15 parts by weight of calcium sulfate whiskers, (e) 0.5 to 3 parts by weight of diantimony trioxide and (f) 0 to 15 parts by weight of other inorganic fillers (however, the sum of (a) to (f) is 100 parts by weight), and thermal decomposition An inorganic foam characterized in that a foaming agent and an aromatic hydrocarbon solvent are kneaded, the kneaded product is heated and cooled in a pressurized mold, and then foamed by decompression. Production method.