JPH0450936B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] This invention relates to a method for producing flame-retardant thermoplastic resin foam. [Conventional technology] Resin foam has excellent insulation properties and is used as a building material and in various other fields, but there is a growing demand for noncombustible materials to prevent the spread of fire and protect human life, and legal regulations are gradually increasing. It is being strengthened. By the way, in order to make a resin molded article flame retardant, it is well known to add a large amount of inorganic matter to the resin or add a flame retardant to the resin before molding. However, in the case of resin foams, when large amounts of inorganic substances are added, the foamability deteriorates, and it is difficult to obtain a closed cell structure, and a flame retardant alone cannot provide sufficient flame retardancy. Therefore, JP-A-56-116727, JP-A-59-
Publication No. 81345 states that the main component of the resin is vinyl acetate.
It has been proposed to use ethylene copolymers to produce closed cell flame retardant foams. [Problems to be solved by the invention] In the conventional method described above, when the vinyl acetate content of the vinyl acetate-ethylene copolymer becomes 20% or more,
The tackiness increases, making it difficult to take off the foam, making it difficult to form the foam, and it also tends to thermally decompose at high temperatures and generate free acetic acid, which deteriorates the resin during melt-kneading and deteriorates the physical properties of the foam. There are drawbacks that reduce it. In addition, vinyl acetate-ethylene copolymers with a vinyl acetate content of less than 20% are crystalline resins, so they do not have sufficient adhesion to the inorganic material they are filled with, resulting in poor physical properties and poor foamability. Closed cell foam is difficult to mold. The present invention aims to provide a method for producing a flame-retardant resin foam that eliminates the disadvantages of using the vinyl acetate-ethylene copolymer described above. [Means for Solving the Problems] This invention uses an ethylene-vinyl acetate-carbon monoxide terpolymer alone having a carbon monoxide content of 2 to 15% by weight as a resin component, or By using a resin component in which a copolymer is mixed with other resins, the problems of the above-mentioned vinyl acetate-ethylene copolymer as the main resin component can be solved. That is, the present invention provides an ethylene-vinyl acetate-carbon monoxide ternary copolymer having a carbon monoxide content of 2 to 15% by weight, or a resin content of 100 parts by weight of the terpolymer mixed with other resins. In contrast, hydrated metal oxides
A flame-retardant resin foam characterized in that a composition consisting of 70 to 300 parts by weight, 10 to 40 parts by weight of a halogen flame retardant, and a pyrolyzable chemical foaming agent is crosslinked with ionizing radiation and then heated and foamed. This is a manufacturing method. The resin component in this invention is an ethylene-vinyl acetate-carbon monoxide terpolymer having a carbon monoxide content of 2 to 15%, or a mixture of the terpolymer and another resin. This terpolymer has a melt index (hereinafter referred to as MI) at 190°C in the range of 0.1 to 40 g/10 minutes, and a density of 0.96 to 1.2 g/10 minutes.
Those in the cm ² range are preferably used. It is also possible to blend other thermoplastic resins with this terpolymer, and blending a crystalline thermoplastic resin has the advantage of improving flexibility and adhesion. In particular, when used as a heat insulating folded plate by attaching it to a folded plate, considering that the flame-retardant resin foam and steel plate are bonded by machine, low-density polyethylene,
The effect is remarkable when blending linear low density polyethylene and high density polyethylene. Among these, linear low-density polyethylene is particularly preferred, with an MI of 0.2 to 20 g/10 min and a density of 0.900 to
^0.930gcm2 is preferred. The hydrated metal oxides used in this invention exhibit flame retardant action when dehydrated by heating, and include aluminum hydroxide, magnesium hydroxide, calcium hydroxide, basic magnesium carbonate, heart clay, talc, and mica. , kaolin clay, asbestos, hydrated calcium silicate, attapulgite, etc. may be used alone or in combination of two or more. The temperature at which aluminum hydroxide is heated and dehydrated is lower than the flash temperature of the resin component ethylene-vinyl acetate-carbon monoxide terpolymer, which exhibits excellent flame retardancy when mixed. Aluminum oxide is preferably used. These hydrated metal oxides are usually used in the form of fine powder, and their average diameter is from 0.01 to 0.01 in terms of expansion ratio.
20μ, preferably 0.05 to 10μ is used. The amount added is based on 100 parts by weight of resin.
70 to 300 parts by weight. This is because if it is less than 70 parts by weight, it will not be possible to reduce smoke generation and combustion heat, and if it exceeds 300 parts by weight, it will not be possible to obtain a foam with sufficient magnification. The halogen flame retardants used in the method of this invention include halogenated aromatic, halogenated resin/aromatic, and halogenated alicyclic flame retardants, such as decabrom diphenyl ether, Hexabromobenzene, Tris (2,
3-dibromopropyl) isocyanurate,
2,2-bis(4-hydroxy-3,5 dibromophenyl)propane and the like are used, and decabromodiphenyl ether is particularly effective. The amount of these halogen flame retardants added depends on the resin content.
The amount is 10 to 40 parts by weight per 100 parts by weight, and if it is less than 10 parts by weight, sufficient flame retardancy will not be exhibited, and if it exceeds 40 parts by weight, it will be uneconomical in terms of cost. Moreover, antimony trioxide, zinc borate, red phosphorus, etc. may be used in combination with the flame retardant as a flame retardant aid. Further, as the blowing agent, a thermally decomposable chemical blowing agent such as azocarbonamide, sodium bicarbonate, dinitrosopentamethylenetetramine, p,p-oxybisbenzenesulfonylhydrazine is used. The amount of foaming agent added varies depending on the desired density of the foam, but
Usually 10-50 copies. The density of the resulting foam is usually about 0.1 to 0.02 g/cm ² . In this invention method, ionizing radiation is irradiated as a means of crosslinking the resin. Ionizing radiation includes electron beams, gamma rays, X-rays,
Although there are neutron beams and the like, electron beams are most preferably used, and the irradiation dose is usually in the range of 1 to 5 Mrad. In addition, various additives such as antioxidants, colorants, carbon black, processing aids such as lubricants, and inorganic surface treatment agents can be used as required. In the method of this invention, a blend consisting of the aforementioned resin, hydrated metal oxide, halogenated flame retardant, blowing agent, and other additives such as flame retardant aids is mixed in a Banbury mixer, kneader or two roll mill. A foamable sheet is formed by mixing the mixture and pelletizing it, or by extruding it using an extruder without pelletizing it. After crosslinking this foamable sheet by irradiating it with an electron beam, it is introduced into a heating device such as an air constant temperature bath, a hot air oven, or a molten salt bath, and is heated and foamed. [Function and Effects] The method of this invention is characterized by using an ethylene-vinyl acetate-carbon monoxide ternary copolymer with a carbon monoxide content of 2 to 15% by weight as the resin component,
Since the above terpolymer generates free acetic acid at a temperature 20°C or more higher than that of conventional ethylene-vinyl acetate copolymers, less free acetic acid is generated during heating and mixing. Therefore, there is no deterioration of the resin during molding, and almost no decrease in strength is observed even when a large amount of hydrated metal oxide and other additives are added. In addition, since the adhesiveness is low, the foamable sheet is easy to handle and is excellent during molding. In addition, since the above terpolymer forms a network structure in the presence of an amine compound, by using a thermally decomposable blowing agent such as azodicarbonamide, crosslinking can proceed even when the blowing agent is thermally decomposed, which is advantageous. It is. Although the foam obtained by the method of this invention is a foam of flammable thermoplastic resin, it is possible to add a hydrated metal oxide and a halogen flame retardant to the above-mentioned terpolymer in combination. Therefore, it exhibits a high degree of flame retardancy and low smoke emission. That is, JIS A applies to heat-insulating folded plates such as colored iron plates, galvanized iron plates, etc., in which the foam obtained by the method of this invention is adhered.
1321-1975 "Flame retardant test method for building interior materials and construction methods" As a result of a combustion test according to the surface test in Section 3, the smoke emission coefficient CA, which indicates the amount of smoke emitted during combustion, and the smoke emitted by combustion were determined. The time-temperature area tdθ, which indicates the amount of combustion heat, is CA 30 or less and tdθ=
0 and satisfies other requirements, resulting in "Class 1 flame retardant"
According to the Ministry of Construction's notification, it is equivalent to ``noncombustible materials''). The effect is demonstrated in the examples described below. [Example] (Examples 1 to 4, Comparative Example 1) Carbon monoxide content is 3% by weight, density is 1.00g/
cm ² , MI20g/min ethylene-vinyl acetate-carbon monoxide terpolymer (manufactured by Dupont; Elvaloy
944) 100 parts by weight, aluminum hydroxide fine powder (Showa Metal Hygilite H-42M) 50-200 parts by weight,
Foaming agent azodicarbonamide 23 parts by weight, flame retardant aid antimony trioxide 3 parts, smoke prevention agent zinc borate 3 parts by weight
A composition consisting of parts by weight and further 1 part by weight of a phenolic antioxidant was kneaded using a mixing roll whose temperature was adjusted to 100 to 110°C, and press-molded at 120°C into a sheet having a thickness of 1.5 mm. This sheet was irradiated with a dose equivalent to an absorbed dose of 2.3 Mrad using an electron beam accelerator. Next, this sheet was placed in a hot air dryer whose temperature was adjusted to 230°C and foamed. The properties and flame retardant test results of the foamed sheet thus obtained are as shown in Table 1. In addition, for the flame retardancy test, foam sheet specimens were placed in a 22cm x
It was cut to a size of 22 cm, heated and laminated to a galvanized iron plate of the same size and 0.8 mm thick, and a surface test was conducted according to the method specified in JIS A-1321-1975.

【table】

[Table] (Examples 5 to 15, Comparative Examples 2 to 3) 100 parts by weight of the same ethylene-vinyl acetate-carbon monoxide ternary copolymer as in Examples 1 to 4, fine aluminum hydroxide powder (manufactured by Showa Light Metal Co., Ltd.) Higilite H-
42M) or 100 parts by weight of magnesium hydroxide fine powder (Kisuma 5B manufactured by Kyowa Chemical Industry Co., Ltd.), 25 parts by weight of azocarbonamide blowing agent, didecabromodiphenyl ether flame retardant, antimony trioxide flame retardant aid, and smoke prevention agent. Blending zinc borate in the proportions shown in Table 2,
Foamed sheets were created in the same manner as Examples 1-4. The properties and flame retardant test results of the foamed sheet thus obtained are as shown in Table 3.

【table】

[Table] (Examples 16 to 28, Comparative Examples 4 to 12) To 100 parts by weight of the resin composition shown in Table 4, 100 parts by weight of aluminum hydroxide fine powder (Hygilite H-42M manufactured by Showa Light Metal Co., Ltd.), flame retardant 25 parts by weight of decabromodiphenyl ether, 3 parts by weight of antimony trioxide as a flame retardant aid, 3 parts by weight of smoke-proofing agent zinc borate, 25 parts by weight of azocarbonamide blowing agent, and 1 part by weight of a phenolic antioxidant. Foamed sheets were created in the same manner as Examples 1-4. The properties and flame retardancy tests for this foamed sheet were conducted in the same manner as in Examples 1 to 4. In addition, an adhesion test was conducted on the foamable sheet before foaming. The adhesion test was performed by applying a load of 1 kg per 25 cm ² of foam sheet onto two layers of the same foam sheet.
After leaving it on for 10 minutes, the load was removed and the adhesive sheet was peeled off by hand. The peel resistance at that time was evaluated in three levels based on sensory evaluation. The test environment conditions were 23°C and 65% RH. Furthermore, among the formulations shown in Table 4, Examples 16, 18,
The formulations of Nos. 19, 21 to 29 and Comparative Example 6 were kneaded using a Banbury mixer, formed into pellets, extruded into a sheet with a thickness of 2.5 mm and a width of 400 mm using a 65 mm single screw extruder, and crosslinked using an electron beam accelerator. Next, this foamable sheet was put into a vertical foaming machine to obtain a long foamed sheet. This foam sheet was sliced to a thickness of about 4 mm to obtain a foam sheet having a skin on only one side. This sample was heated and adhered to a galvanized iron plate with a thickness of 0.8 mm. Next, this composite was folded into a folded plate using a one- to three-fold folding plate bending machine. The state of damage to the foam sheet at that time was observed. The test results were as shown in Tables 5 and 6. In addition, Evasuren 450P in Table 4 is
Ethylene-vinyl acetate copolymer with vinyl acetate 61% by weight and MI 30-50 (manufactured by Dainippon Ink Company), Table 4
Those marked with * for LDPE or L-LDPE are
It is L-LDPE with MI8 and density 0.920, and the unmarked one shows LDPE with MI4 and density 0.924. Furthermore, the * and ** marks in the Evathrene column are Mitsui Pochemical's Evaflex 40X and 45X, *3 is a partially saponified ethylene-vinyl acetate copolymer (Dyumilan C-1570, manufactured by Takeda Pharmaceutical Co., Ltd.), and *4 is Ethylene-α-olefin copolymer (Tafmer 880P
(manufactured by Mitsui Petrochemical).

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Claims (1)

[Claims] 1. Ethylene with a carbon monoxide content of 2 to 15% by weight
70 to 300 parts by weight of a hydrated metal oxide per 100 parts by weight of the vinyl acetate-carbon monoxide terpolymer or the resin content of the terpolymer mixed with another resin;
1. A method for producing a flame-retardant resin foam, which comprises crosslinking a composition comprising 10 to 40 parts by weight of a halogen flame retardant and a pyrolyzable chemical foaming agent with ionizing radiation and then heating and foaming the composition. 2 The ratio of ethylene-vinyl acetate-carbon monoxide terpolymer to the total resin content is 20 to 100% by weight
A method for producing a flame-retardant resin foam according to claim 1. 3. The method for producing a flame-retardant resin foam according to claim 1 or 2, wherein the other resin is linear low-density polyethylene. 4. The method for producing a flame-retardant resin foam according to claim 3, wherein the linear low-density polyethylene has a melt index of 0.2 to 20 g/min and a density of 0.900 to 0.930 g/ ^cm2 .