JPH0892406A - Flame-retardant polyolefinic resin foam - Google Patents

Abstract

PURPOSE: To obtain a polyolefin resin foam which is safe and excellent in flame retardancy, does not discolor in the molding step, and is excellent in moldability and heat resistance. CONSTITUTION: This foam comprises 100 pts.wt. polyolefinic resin and 1-50 pts.wt. ethylenebispentabromodiphenyl as a flame retardant. It is desirable that the above polyolefinic resin is a mixture comprising 50-95wt.% polypropylene resin having a melt index of 0.5-20g/10min and a melting point of 130-170 deg.C and 50-5wt.% polyethylene resin having a density of 0.940g/cm<3> or below.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame-retardant polyolefin-based resin foam, and more specifically, it is safe and flame-retardant without producing teratogenic substances, and can be colored during molding. Not related to polyolefin resin foam.
The present invention also relates to a polyolefin-based resin foam having excellent flame retardancy, molding processability, and heat resistance. INDUSTRIAL APPLICABILITY The foam of the present invention can be used in a wide variety of fields such as heat insulating materials, vacuum / pneumatic molded products, and vehicle interior materials.

[0002]

2. Description of the Related Art Polyolefin resin foams are usually
A thermal decomposition type foaming agent is blended with a polyolefin resin, and the mixture is melted and kneaded at a temperature not higher than the decomposition temperature of the foaming agent, molded into a desired shape such as a sheet, and then crosslinked as desired, and then a molded body is formed. It is produced by heating above the decomposition temperature of the foaming agent to foam. Polyolefin resin foams are used in a wide range of fields as heat insulating materials, cushioning materials, and the like. For example, polyolefin resin foams are used as heat insulating materials and interior materials for ceilings, doors, instrument panels, cooler covers, etc. in automobile applications. In addition, the polyolefin resin foam,
It is used as a heat insulating material and cushioning material in building materials, furniture, household appliances, etc.

These heat insulating materials and the like are generally commercialized by forming (secondary processing) a polyolefin resin foam sheet into a predetermined shape by a thermoforming method such as vacuum forming or compression forming. In the case of an automobile interior material, a soft vinyl chloride resin sheet is laminated as a skin material on the surface of a polyolefin resin foam sheet, and is molded and processed as a composite material. These forming processes are performed under high temperature conditions, and often deep drawing is performed. Therefore, the polyolefin resin foam is required to have excellent moldability and heat resistance. Since the polyolefin resin foam is used as an interior material or the like, it is desirable that the polyolefin resin foam is not colored (discolored).

On the other hand, the polyolefin resin foam is flammable. Therefore, flame retardancy is required in the field where flame retardancy is required such as building materials. Conventionally,
The flame-retardant method of the polyolefin resin foam is, for example, a method of adding decabromodiphenyl oxide as a flame retardant (JP-A-51-134762 and JP-A-51).
No. 146565) has been proposed. However, it has been pointed out that decabromodiphenyl oxide produces dioxin, which has a toxic and teratogenic effect when it is burned.

Tetrabromobisphenol A, which is a general-purpose flame retardant, has a low heat resistance, so that there is a problem that the foam is colored under high temperature conditions during foaming. Moreover, many conventional flame retardants, including these halogen-based flame retardants, have to be blended in relatively large proportions in order to impart sufficient flame retardancy to the polyolefin resin foam. However, when a large amount of flame retardant is added, the moldability of the polyolefin resin foam deteriorates, and the foam breaks or uneven thickness occurs.

JP-A-59-115340 discloses a mixture of a polypropylene resin (A) and a polyethylene (B) having a melting point of 115 to 130 ° C. and a density of 0.940 g / m ³ or less as a flame retardant. Flame-retardant polypropylene foams containing bisguanidinium tetrabromophthalate have been proposed. This flame-retardant polypropylene foam is said to have excellent flame retardancy and thermoformability.
However, since the flame retardant lowers the decomposition temperature of the thermal decomposition type foaming agent, when the resin composition containing the flame retardant is extruded, the foaming agent is easily decomposed to obtain a satisfactory foamable sheet. There was a problem that I could not. In particular,
A polypropylene resin having a high melting point needs to be melt-kneaded and extruded at a relatively high temperature, and therefore a polypropylene resin composition containing a flame retardant that lowers the thermal decomposition temperature of a foaming agent is extruded. It is difficult to make a foamable sheet. Therefore, it was difficult to obtain a flame-retardant polyolefin resin foam excellent in moldability and heat resistance.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyolefin resin foam which is safe, has excellent flame retardancy, and does not color during molding. Another object of the present invention is to provide a polyolefin resin foam excellent in flame retardancy, moldability and heat resistance. The present inventors have conducted extensive studies to overcome the problems of the prior art, and as a result, when ethylenebispentabromodiphenyl is used as a flame retardant, it does not generate teratogenic substances, is safe, and is flame retardant. It has been found that a polyolefin resin foam which is excellent and does not color during molding can be obtained.

Further, when ethylenebispentabromodiphenyl is used as the flame retardant, even when a polyolefin resin composition containing a large proportion of a polypropylene resin having a high melting point is used as the polyolefin resin, the polyolefin resin composition can be used during molding. It was found that a thermal decomposition type foaming agent is hard to decompose and a foam having excellent flame retardancy, moldability and heat resistance can be obtained. This ethylenebispentabromodiphenyl can exert a high flame retarding effect by using a relatively small amount as compared with conventional flame retardants. The present invention has been completed based on these findings.

[0009]

According to the present invention, a flame-retardant polyolefin resin foam formed by adding 1 to 50 parts by weight of ethylenebispentabromodiphenyl as a flame retardant to 100 parts by weight of a polyolefin resin. The body is provided. Further, according to the present invention, (A) the melt index is 0.5 to 20 g / 10 minutes and the melting point is 130 to 1
To 100 parts by weight of a resin component containing 50 to 95% by weight of a polypropylene resin at 70 ° C. and 50 to 5% by weight of (B) a polyethylene resin having a density of 0.940 g / cm ³ or less, ethylene bis as a flame retardant. Provided is a flame-retardant polyolefin-based resin foam containing 1 to 50 parts by weight of pentabromodiphenyl.

The present invention will be described in detail below. Polyolefin Resin The polyolefin resin used in the present invention is a homopolymer or copolymer of olefinic hydrocarbon, and is, for example, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene and butene, or α such as pentene. -Copolymer with olefin, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-styrene copolymer,
Examples thereof include an ethylene-propylene-styrene-butadiene copolymer, an ethylene-vinyl chloride copolymer, and a mixture of two or more of these. These olefin resins may be chemically modified such as grafted. In order to obtain a polyolefin resin foam excellent in moldability and heat resistance at high temperatures, it is preferable to use a resin composition of polypropylene resin (A) and polyethylene resin (B) as the polyolefin resin. .
Hereinafter, each resin component used in the resin composition will be described.

The polypropylene resin (A) used in the present invention is generally a homopolymer of crystalline polypropylene having good stereoregularity polymerized by a Ziegler type catalyst, and the content of propylene is 70% by weight or more, preferably 85%. It is a polypropylene copolymer of not less than wt% or a mixture of two or more thereof. Examples of the polypropylene copolymer include a copolymer of polypropylene and α-olefin. Examples of the α-olefin include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like.
Moreover, a propylene-ethylene copolymer can also be used. The polypropylene resin (A) needs to have a melt index (MI) of 0.5 to 20 (g / 10 minutes) and a melting point of 130 to 170 ° C.
When the MI is less than 0.5, a problem in appearance occurs when it is formed into a sheet by extrusion molding, and when it exceeds 20, the heat resistance becomes insufficient. If the melting point is less than 130 ° C, the heat resistance becomes insufficient, and if it exceeds 170 ° C, it is difficult to synthesize.

Among these polypropylene resins,
Ethylene content 2-5% by weight, melting point 140-150
C., random polypropylene having MI of 0.5 to 3.0,
Alternatively, the ethylene content is 5 to 10% by weight and the melting point is 15
A block polypropylene having a MI of 3.0 to 7.0 at 0 to 165 ° C. is particularly preferable. The polyethylene resin (B) used in the present invention is a polyethylene homopolymer, a copolymer containing ethylene as a main component, or a mixture of two or more thereof. As the ethylene copolymer, an ethylene-α-olefin copolymer containing 80% by weight or more of ethylene units is preferable. Examples of the α-olefin include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like.

The polyethylene resin (B) used in the present invention must have a density of 0.940 g / cm ³ or less. Those having a density of more than 0.940 g / cm ³ have a small effect of improving the elongation of the foam even when blended with the polypropylene resin (A). The lower limit of the density is preferably 0.915 g / cm ^{3 in} terms of the appearance of the foam. MI
Is usually 0.5 to 50 (g / 10 minutes). Among polyethylene resins, the density is 0.920 to 925 g /
cm ³ , MI of 2.0 to 8.0, melting point of 120 to 123
Linear low density polyethylene at 0 ° C. is particularly preferred. The mixing ratio (A: B) of the polypropylene resin (A) and the polyethylene resin (B) is 50:50 to 95: 5 (weight ratio), preferably 60:40 to 90:10. By using these resin components within the range of the above blending ratio, it is possible to obtain a foam having good physical properties at high temperatures such as heat resistance, molding processability, and appearance.

Flame Retardant The flame retardant used in the present invention is ethylene bispentabromodiphenyl represented by the following formula.

[0015]

[Chemical 1] Ethylenebispentabromodiphenyl is a resin component 10
1 to 50 parts by weight, preferably 2 to 3 relative to 0 parts by weight
Used in the range of 0 parts by weight. If this blending ratio is too small, a sufficient flame retarding effect cannot be obtained, and if it is too large, it becomes difficult to obtain a satisfactory foamed product due to gas escape during foaming.

Ethylene bispentabromodiphenyl is
It contains 10 bromine atoms in the molecule, and the content of bromine atoms is 82%, which is 83% that of decabromodiphenyl oxide.
It is almost equal to%. As described above, it can be considered that the high content of bromine atom is the reason why the excellent flame retarding effect can be obtained with the addition of a relatively small amount. Further, since ethylenebispentabromodiphenyl has a high melting point of 345 ° C. and a high thermal decomposition temperature of 370 ° C., it does not melt or decompose at the molding temperature and the foaming temperature. Therefore, ethylenebispentabromodiphenyl does not bleed out to the surface of the foam. In addition, ethylenebispentabromodiphenyl does not generate a teratogenic substance and does not color the foam during molding. In order to improve the flame retardant effect, a flame retardant auxiliary agent such as antimony trioxide can be used in combination. The flame retardant aid is usually added in a proportion of 1 to 20 parts by weight with respect to 100 parts by weight of the resin component.

Thermally Decomposable Foaming Agent In the present invention, a thermally decomposable foaming agent is usually added as a foaming agent to a resin composition containing a resin component and a flame retardant. As the thermal decomposition type foaming agent, for example, azodicarbonamide, benzenesulfonyl hydrazide, dinitrosopentamethylenetetramine, toluenesulfonyl hydrazide,
4,4-oxybis (benzenesulfonyl hydrazide)
And so on. These may be used alone,
It is also possible to use two or more types in combination. The thermal decomposition type foaming agent is usually 1 to 100 parts by weight of the resin component.
Within the range of 50 parts by weight, it is used in an appropriate amount depending on the desired expansion ratio.

Other Additives In the present invention, in order to obtain a crosslinked foamed product, a chemical crosslinking agent such as an organic peroxide can be added to the resin component. Further, in order to obtain a crosslinked foamed product, a molded product such as a foamable extruded sheet can be irradiated with ionizing radiation such as an electron beam to be crosslinked. In this case, various crosslinking aids can be added. Examples of the crosslinking aid include polyfunctional monomers such as divinylbenzene, diallyl phthalate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, tetraethylene glycol dimethacrylate and triallyl isocyanurate. These cross-linking aids are usually added in a proportion of 0.5 to 7 parts by weight with respect to 100 parts by weight of the resin component. If desired, antioxidants (phenolic, phosphorus, sulfur, etc.), metal oxides, metal soaps, pigments, low viscosity agents such as low polymerization degree polybutene, etc. may be added to the resin component. Good.

Method for Producing Foam In order to produce the flame-retardant polyolefin resin foam of the present invention, first, a polyolefin resin, ethylenebispentabromodiphenyl, a pyrolytic foaming agent, and other additives are added. Using a single-screw, twin-screw, multi-screw extruder or a kneader such as a Banbury mixer or a pressure kneader, the mixture is melt-kneaded at a temperature lower than the decomposition temperature of the thermal decomposition type foaming agent to form a desired shape. . The respective components may be mixed in advance or may be separately supplied to the kneader. As a molding machine,
An extruder is preferably used. You may press-mold.
The shape of the molded body may be a sheet shape, a rod shape, or the like, but is usually formed into a sheet shape.

In order to obtain a crosslinked foamed product, the obtained foamable molded product is irradiated with ionizing radiation to be crosslinked. Examples of the ionizing radiation include α rays, β rays, γ rays, neutron rays, electron beams and the like. The irradiation dose is usually 1 to 20 Mrad. It is also possible to add an organic peroxide in advance and chemically crosslink. Then, the foamable molded article is heated to a temperature equal to or higher than the decomposition temperature of the thermal decomposition type foaming agent to foam, whereby a foamed article can be obtained. For foaming, a vertical hot air foaming furnace,
A horizontal hot air foaming furnace, a salt bath, a metal bath, or a combination of these with a heater can be used.

Polyolefin-based resin foam The flame-retardant polyolefin- based resin foam of the present invention is a foam having a good appearance, is colored safely, does not generate teratogenic substances, and is safe and flame-retardant. It is a foam with excellent properties. Polyolefin resin (polypropylene resin) using a resin composition of polypropylene resin (A) and polyethylene resin (B) as the polyolefin resin
The foam is excellent in flame retardancy, heat resistance, and moldability, and in particular, it can be secondarily processed into a molded product having a complicated and deep shape without being damaged during molding at high temperature. Further, even if a relatively small amount of a flame retardant is added, good flame retardancy is exhibited, and it is possible to form a sheet having a good appearance under high temperature conditions even when forming an expandable molded article.

[0022]

EXAMPLES The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The methods for measuring physical properties are as follows. <Oxygen index> Measured according to JIS K-7201. <APHA> The color tone (coloring degree) according to the platinum-cobalt standard is measured according to the evaluation standards of the American Public Health Association. <Elongation> Add 5 sheets of foam sheet to the heat insulation box set to 160 ℃.
After being left for a minute, it was measured by a tensile tester (JIS K-
6767). MD: sheet extrusion direction, TD: vertical direction to sheet extrusion direction.

[Examples 1 to 4] Polyethylene resin (M
I = 2.0 g / 10 min, density 0.920 g / cm ³ ) 1
Azodicarbonamide (ADCA) 20 is added to 00 parts by weight.
Parts by weight, zinc stearate 2.5 parts by weight, and ethylene bispentabromodiphenyl (manufactured by Ethyl Co., trade name Sa
ytex8010) was mixed in the ratio shown in Table 1 and melt-kneaded by a plastograph. This was molded into a sheet having a thickness of 3.0 mm by a hot pressing method, the sheet was irradiated with an electron beam having a dose of 5.0 mrad to be crosslinked, and then foamed in a heating oven at 210 ° C. did. The obtained foams all had a uniform appearance. The oxygen index of each foam was measured by a conventional method. The larger the oxygen index, the better the flame retardancy. The polyethylene resin foam to which the flame retardant was not added had an oxygen index of about 18. In addition, for each foam, APHA was measured in order to check the degree of coloring. The larger this value, the darker the color. APHA of 20 indicates a white foam, and 100 indicates a brown color. When APHA is 30 or more, coloring is recognized. The results are shown in Table 1.

[Examples 5 to 6] Polyethylene resin (M
I = 2.0 g / 10 min, density 0.920 g / cm ³ ) 1
20 parts by weight of azodicarbonamide, 2.5 parts by weight of zinc stearate, 30 parts by weight of ethylenebispentabromodiphenyl, and 30 parts by weight of antimony trioxide were mixed with 00 parts by weight in a ratio shown in Table 1 and melt-kneaded by a plastograph. did.
This was formed into a sheet having a thickness of 3.0 mm by a hot pressing method, and the sheet was irradiated with an electron beam irradiation device at a dose of 5.0 mrad.
Was irradiated with the electron beam to crosslink, and then foamed in a heating oven at 210 ° C. The obtained foams all had a uniform appearance. Table 1 shows the measurement results of physical properties. When ethylene bispentabromodiphenyl and antimony trioxide are used together, the oxygen index is further improved, and better flame retardancy is exhibited.

COMPARATIVE EXAMPLE 1 Except that the mixing ratio of ethylenebispentabromodiphenyl was 0.5 part by weight.
Foams were prepared in the same manner as in Examples 1 to 4. The results are shown in Table 1. The obtained foam had a small oxygen index value because the blending ratio of ethylenebispentabromodiphenyl was small, and was inferior in the flame retarding effect.

COMPARATIVE EXAMPLE 2 An attempt was made to make a foam in the same manner as in Examples 1 to 4 except that the mixing ratio of ethylenebispentabromodiphenyl was 60 parts by weight. However, it was not possible to obtain a good foam because the moldability was poor and gas was released. The results are shown in Table 1.

[Comparative Examples 3 to 5] As a flame retardant, tetrabromobisphenol A (manufactured by Tosoh Corporation, trade name: Flame Cut 120R) was used in a blending ratio shown in Table 1 instead of ethylenebispentabromodiphenyl. Is
Foams were prepared in the same manner as in Examples 1 to 4. The results are shown in Table 1. These foams were highly colored.

[0028]

[Table 1] (Footnote) EB: Ethylenebispentabromodiphenyl TB: Tetrabromobisphenol A

[Examples 7 to 9] 70 parts by weight of polypropylene resin (MI = 2.0, mp = 146 ° C., random), linear low density polyethylene (MI = 2.0, mp = 1)
At 20 ° C., density = 0.920 g / cm ³ ) 30 parts by weight, azodicarbonamide 10 parts by weight, divinylbenzene 3 parts by weight, and ethylenebispentabromodiphenyl are shown in Table 2.
120m in diameter after mixing and mixing evenly
Using a twin-screw extruder in the same direction with mφ and L / D = 40, the resin was extruded at a resin temperature of 186 ° C. to form a sheet having a thickness of 1.5 mm. Next, this sheet was irradiated with an electron beam of 3 Mrad to be crosslinked, and then foamed in a hot air oven at 290 ° C. The obtained foam had a good cell shape, a thickness of 3.0 mm, and a foaming ratio of 25 times. The oxygen index and the elongation at 160 ° C. of this foam were measured, and the results are shown in Table 2.

Comparative Examples 6 to 8 Foams were prepared in the same manner as in Examples 7 to 9 except that tetrabromobisphenol A was used as the flame retardant instead of ethylenebispentabromodiphenyl. The physical properties were measured. Table 2 shows the results.

[0031]

[Table 2] (Footnote) EB: Ethylenebispentabromodiphenyl TB: Tetrabromobisphenol A ADCA: Azodicarbonamide

Examples 10 to 11 Polypropylene resin (MI = 4.0, mp = 164 ° C., block) 60 parts by weight, polyethylene resin (MI = 4.0, mp = 12)
0 ° C., density = 0.920 g / cm ³ ) 40 parts by weight, divinylbenzene 3 parts by weight, azodicarbonamide 10 parts by weight, and ethylene bispentabromodiphenyl as a flame retardant were mixed in a ratio shown in Table 3, and a diameter was obtained. 70 mmφ, L
A sheet was prepared by extruding at a resin temperature of 185 ° C. using a twin-screw extruder of / D = 36. 3Mrad on this sheet
After irradiating with the electron beam of No. 3, the foam was foamed in a hot air oven at 290 ° C. The oxygen index of the foam thus obtained was measured, and the results are shown in Table 3.

[Comparative Example 9] A foam was prepared in the same manner as in Examples 10 to 11, except that the mixing ratio of ethylenebispentabromodiphenyl was 60 parts by weight. However, it was not possible to obtain a foam by degassing during foaming.

[Comparative Examples 10 to 12] Foaming was carried out in the same manner as in Examples 10 to 11, except that decabromodiphenyl oxide was used as the flame retardant in place of ethylenebispentabromodiphenyl in the ratio shown in Table 3. Created the body. In Comparative Example 12, outgassing occurred and no foam was obtained. The results are shown in Table 3.

[0035]

[Table 3] (Footnote) (* 1) Gas was released and no foam was obtained. EB: ethylene bispentabromodiphenyl DB: decabromodiphenyl oxide ADCA: azodicarbonamide

[Example 12] Polypropylene resin (M
I = 0.5, mp = 150 ° C., random) 70 parts by weight,
Polyethylene resin (MI = 2.0, mp = 120 ° C.,
Density = 0.920 g / cm ³ ) 30 parts by weight, divinylbenzene 3 parts by weight, azodicarbonamide 10 parts by weight, ethylenebispentabromodiphenyl 10 as a flame retardant
By weight, 2.5 parts by weight of antimony trioxide were uniformly mixed and extruded at a resin temperature of 180 ° C. using a biaxial extruder having different diameters of 100 mmφ and L / D = 21 to obtain a sheet. The sheet was irradiated with an electron beam of 3 Mrad to be crosslinked, and then placed in a hot air oven at 290 ° C. for foaming to obtain a foam having a thickness of 2.5 mm and a foaming ratio of 25 times.
The oxygen index of this foam was 29.

[Comparative Example 13] A sheet was prepared in the same manner as in Example 12 except that bisguanidinium tetrabrom phthalate was used as the flame retardant instead of ethylene bispentabromodiphenyl. The foaming agent decomposed and a sheet could not be obtained. Even when the resin temperature was lowered to 170 ° C. and extruded, the primary decomposition of the foaming agent did not subside and an extruded sheet could not be obtained.

[0038]

Industrial Applicability According to the present invention, there is provided a polyolefin resin foam which does not generate teratogenic substances, is safe, has excellent flame retardancy, and does not become colored during molding.
Further, according to the present invention, there is provided a polyolefin resin foam excellent in molding processability, heat resistance and flame retardancy. In the present invention, since ethylenebispentabromodiphenyl is used as the flame retardant, it is possible to carry out extrusion molding without primary decomposition of the foaming agent during extrusion molding. Therefore, even if a polypropylene resin having a high melting point is used, a flame-retardant polyolefin resin foam having satisfactory physical properties can be obtained.

Claims (2)

[Claims] 1. A flame-retardant polyolefin resin foam comprising 100 parts by weight of a polyolefin resin and 1 to 50 parts by weight of ethylenebispentabromodiphenyl as a flame retardant. 2. The polyolefin resin (A) has a melt index of 0.5 to 20 g / 10 minutes, a melting point of 130 to 170 ° C. and a polypropylene resin of 50 to 95% by weight, and (B) a density of 0. The flame-retardant polyolefin resin foam according to claim 1, which contains 50 to 5% by weight of a polyethylene resin of not more than 940 g / cm ³ .