JPH05320399A - Flame-retardant resin foam composition, flame-retardant material, flame-retardant resin foam, and method for producing flame-retardant resin foam - Google Patents

Abstract

(57) [Summary] [Structure] A composition for a flame-retardant resin foam containing a polyolefin resin and a flame-retardant material. The flame retardant material includes core particles made of a flame retardant and a foaming agent layer coating the core particles. [Effect] A flame-retardant resin foam having small flame-retardant anisotropy can be obtained.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a resin foam composition,
Flame-retardant material, resin foam and method for producing resin foam, in particular,
Flame-retardant resin foam composition, flame-retardant material used therein,
The present invention relates to a flame-retardant resin foam and a method for producing a flame-retardant resin foam.

[0002]

2. Description of the Related Art In general, polyolefin resin foams are lightweight and have excellent heat insulation and sound insulation properties, so that they are used in the fields of building materials, industrial materials, daily necessities and interior materials for vehicles. Widely used. However, since polyolefin resins are easily burned, various studies have been made to make them flame-retardant. For example, as a flame-retardant polyolefin resin foam, a flame retardant containing a halogenated aromatic compound such as decabromodiphenyl ether or hexabromobenzene and a flame retardant auxiliary such as antimony trioxide, or tetrabromobisphenol A glycidyl ether. It is known to add epoxy flame retardants such as.

[0003]

In the conventional flame-retardant polyolefin resin foam, the dispersion state of the flame retardant changes during crosslinking / foaming, and as a result, the entire foam is uniform and stable flame retardant. May not show sex. That is, anisotropy of flame retardancy or insufficient flame retardancy may occur.

It is an object of the first, second, third and fourth inventions to provide a flame retardant resin foam composition capable of forming a flame retardant resin foam having a small anisotropy. .. Fifth,
It is an object of the sixth and seventh inventions to provide a flame-retardant material that can impart flame retardancy with small anisotropy to a resin foam.
An object of the eighth invention is to provide a flame-retardant resin foam having a small flame-retardant anisotropy.

An object of the ninth invention is to provide a method for producing a flame-retardant resin foam according to the eighth invention.

[0006]

The composition for a flame-retardant resin foam according to the first invention contains a polyolefin resin and a flame-retardant material. The flame retardant material includes core particles made of a flame retardant and a foaming agent layer coating the core particles. The composition for a flame-retardant resin foam according to the second invention has a density of 0.910 to 0.930 g / cm ³ and a melt flow rate of 0.1 as the polyolefin resin used in the first invention. A low density polyethylene resin of 5 to 50 g / 10 minutes is used.

The composition according to the third invention uses, as the low density polyethylene resin used in the second invention, a low density polyethylene resin containing less than 90% by weight of another polyolefin resin. A composition for a flame-retardant resin foam according to a fourth aspect of the invention is an ethylene-based resin containing 2 to 5% by weight of ethylene as the polyolefin-based resin used in the first aspect of the invention.
Propylene copolymer 50-90% by weight and density 0.8
A polymer containing 90 to 0.930 g / cm ³ of ethylene-α-olefin copolymer and 50 to 10% by weight is used.

The flame retardant material according to the fifth aspect of the present invention comprises core particles made of a flame retardant and a foaming agent layer coating the core particles. The flame-retardant material according to the sixth invention uses, as the flame-retardant agent used in the fifth invention, one having a melting point, a softening point or a glass transition temperature of 150 to 250 ° C.

The flame retardant material according to the seventh invention is a halogenated phosphorus compound-containing flame retardant containing 30 to 80% by weight of phosphorus and halogen in total as the flame retardant used in the fifth or sixth invention. I am using. In the flame-retardant resin foam according to the eighth aspect of the present invention, a coating film made of a polyolefin resin and substantially made of a flame retardant is formed on the inner surface of the cells.

The method for producing a flame-retardant resin foam according to the ninth aspect of the invention includes the following steps. A step of molding a composition for a flame-retardant resin foam, which comprises a polyolefin resin and a flame-retardant material in which core particles made of a flame retardant are coated with a foaming agent. ◎ A step of heating the molded composition for flame-retardant resin foam to crosslink and foam. ************ Polyolefin Resin A low density polyethylene resin can be exemplified as the polyolefin resin used in the present invention. Low density polyethylene resin has a density of 0.910 to 0.930 g / c
m ³ (more preferably 0.920 to 0.925 g / cm
³ ) and a melt flow rate of 0.5 to 50 g /
It is preferably 10 minutes. Density is 0.910g / cm ³
If it is less than the above range, the crystallinity of the resin will be low, and the mechanical properties of the foam will be reduced. In addition, the composition of the present invention is blocked and becomes difficult to handle in the process of producing a foam. On the other hand, if it exceeds 0.930 g / cm ³ , the crystallinity increases, and it becomes difficult to crosslink. When the melt flow rate is less than 0.5 g / 10 minutes, shearing heat is generated during extrusion, and the foaming agent may decompose. Conversely, 50
If it exceeds g / 10 minutes, it is difficult to obtain a foaming sheet having good flatness unless a special cooling device is used during extrusion.

Other polyolefin resins may be mixed with the above low density polyethylene resin in an amount of less than 90% by weight. When the amount of the other polyolefin-based resin mixed exceeds 90% by weight, it may be difficult to apply various crosslinking methods depending on the mixed resin. Other polyolefin resins include ethylene-propylene copolymer, linear low-density polyethylene, high-density polyethylene, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer. Examples thereof include a polymer, an ethylene-alkyl acrylate copolymer, an ethylene-methaalkyl acrylate copolymer, and a terpolymer obtained by copolymerizing these polyethylene-based copolymers with maleic anhydride as a third component.

Particularly preferred as the polyolefin resin is 50 to 90% by weight of an ethylene-propylene copolymer having an ethylene content of 2 to 5% by weight and a density of 0.890.
~ 0.930 g / cm ³ (more preferably 0.900 to
It is a mixed resin containing 50 to 10 wt% of ethylene-α-olefin copolymer of 0.925 g / cm ³ ). When such a mixed resin is used, a resin foam having excellent flame retardancy, moldability and heat resistance can be obtained. In addition, in this mixed resin, when the ethylene-propylene copolymer is less than 50% by weight and the ethylene-α-olefin copolymer exceeds 50% by weight, the heat resistance of the foam is lowered. on the other hand,
When the ethylene-propylene copolymer is more than 90% by weight and the ethylene-α-olefin copolymer is less than 10% by weight, the propylene component that hinders flame retardation increases, so that a foam having good flame retardancy is obtained. I can't get it. Further, the obtained foam is not good in flexibility and cushioning property.

The polyolefin resin used in the present invention is not limited to the above-mentioned various polyolefin resins. Flame-retardant material The flame-retardant material used in the present invention is obtained by coating core particles made of a flame retardant with a foaming agent.

The flame retardant constituting the core particles has a melting point, a softening point or a glass transition temperature of 150 to 250 ° C., and further 18
The thing of 0-230 degreeC is preferable. When the temperature is lower than 150 ° C., the flame retardant material is irregularly dispersed in the above-mentioned polyolefin resin, which may cause coarse bubbles in the foam. In addition, when the composition of the present invention is formed into a sheet, the flame retardant may bleed out on the surface of the sheet. On the other hand, when the temperature exceeds 250 ° C., it becomes difficult to form a thin film of the flame retardant on the inner surface of the foam.

The flame retardant is not particularly limited as long as it satisfies the above-mentioned conditions such as melting point.
Epoxy flame retardant containing 0% by weight and having a tetrabromobisphenol A skeleton, specifically SR-TBA50
Examples thereof include 00 to 20000 (manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.).

As the flame retardant, a halogenated phosphorus compound-containing flame retardant containing phosphorus and halogen simultaneously in the molecular skeleton, particularly a halogen-containing phosphate ester flame retardant, is particularly preferable. Examples of this type of flame retardant include tris (tribromoneopentyl) phosphate and tris (tribromophenyl) phosphate. In this type of flame retardant, the total content of phosphorus and halogen is 3
It is preferably 0 to 80% by weight, more preferably 50 to 75% by weight.
When the phosphorus and halogen contents are less than 30% by weight,
Since it is necessary to use a large amount of the flame retardant in order to enhance the flame retardancy of the foam, the film of the flame retardant formed on the inner surface of the bubbles of the foam becomes thick. As a result, the cushioning properties of the foam are reduced, and the expansion ratio is reduced. On the other hand, when it exceeds 80% by weight, the stability of the flame retardant is lowered, so that the flame retardancy of the foam is rather lowered, and the film made of the flame retardant cannot be sufficiently formed on the inner surface of the cells of the foam.

The flame retardant has a particle size of 0.2 to 50 μm, preferably 0.5 to 20 μm. When the particle size is less than 0.2 μm, the bulk density of the flame retardant increases accordingly, so the dispersibility of the flame retardant in the polyolefin resin component decreases, and coarse bubbles are easily generated in the foam. .. Also,
Since the flame-retardant material is likely to be secondarily aggregated to form coarse particles, coarse bubbles are easily generated in the foam. Further, since it becomes difficult to control the thickness of the foaming agent coated on the flame retardant, the film of the flame retardant formed on the inner surface of the cells of the foam becomes thin, and the film breaks and the flame retardancy of the foam decreases. Conversely, the particle size is 5
When it exceeds 0 μm, the cell strength of the foam is weakened and the mechanical strength of the foam is lowered. In addition, since the foaming gas due to the foaming agent is likely to dissipate, it is difficult to form a foam having a high expansion ratio and good buffering properties. Further, since the particle size of the flame retardant material becomes large, it is easy to generate coarse bubbles in the foam.

The foaming agent coated on the flame retardant is a decomposable foaming agent. As the decomposable foaming agent, either an organic foaming agent or an inorganic foaming agent may be used.
Examples of organic decomposition-type foaming agents include azodicarbonamide, N, N′-dinitrosopentamethylenetetramine,
P, p'-oxybenzene sulfonyl hydrazide etc. can be illustrated. Examples of the inorganic decomposing type foaming agent include sodium carbonate, ammonium carbonate, ammonium bicarbonate, calcium azide and the like.

The flame-retardant material used in the present invention is preferably particles having a host-guest structure obtained by uniformly coating a foaming agent by the mechanofusion method using the above-mentioned flame retardant as a nucleating agent. Such particles are charged with a flame retardant and a foaming agent in an ong mill consisting of a cylindrical casing and an inner piece having an inner diameter smaller than the inner diameter of the casing and fixed, and the casing is rotated at a high speed for a predetermined time. Then it can be manufactured. The reason why the coating by the mechanofusion method is preferable is considered as follows. That is, the foaming agent coated by the mechanofusion method,
The flame retardant is not simply attached to the surface of the core particles, but is in a state of entering the surface of the core particles, and a strong coating film is formed by mechanochemical bonding such as surface fusion.
As a result, the flame-retardant material maintains its structure even when subjected to shearing force when the composition is prepared by adding it to the polyolefin resin component or when the composition is melt-extruded. It is considered that a stable dispersion state is exhibited, the flame retardant film can be stably formed on the inner surface of the foam, and the foam can be regulated.

In the flame-retardant material, the coating amount of the foaming agent is preferably set to less than 50% by weight of the flame-retardant agent. When the amount is 50% by weight or more, the foaming agent falls off from the flame retardant when the composition of the present invention is prepared, and it becomes difficult to form a uniform film of the flame retardant on the inner surface of the cells of the foam. Flame-retardant resin foam composition In the flame-retardant resin foam composition of the present invention, the amount of the flame retardant added is 2 to 30% by weight in the composition excluding the foaming agent described below ( It is more preferably set to 5 to 25% by weight). If the amount of the flame retardant added is less than 2% by weight, the proportion of the bubbles in which the film made of the flame retardant is formed is reduced, so that the flame retardancy of the foam is reduced. On the other hand, when it exceeds 30% by weight, the film of the flame retardant formed on the inner surface of the bubbles becomes thick, and the cushioning property and other functions of the foam may be impaired.

The composition for flame-retardant resin foam of the present invention may contain a foaming agent in addition to the foaming agent constituting the flame-retardant material. As the foaming agent, the same as the above-mentioned decomposition type foaming agent can be used. Furthermore, in the composition for a flame-retardant resin foam of the present invention, if necessary, a heat stabilizer, a weather resistance agent, a flame retardant auxiliary agent (for example, an antimony compound), a dispersant, a crosslinking agent, a crosslinking auxiliary agent, An inorganic filler or the like may be added. When adding an inorganic filler,
The addition amount is preferably set so that the total amount of the flame retardant and the inorganic filler is less than 50% by weight in terms of the volume fraction of the composition excluding the foaming agent. In this case, a foam having a high expansion ratio can be obtained. Manufacturing Method of Flame-Retardant Resin Foam Here, a case of manufacturing a continuous sheet-shaped flame-retardant resin foam using the above-mentioned composition for flame-retardant resin foam will be described as an example.

First, a flame-retardant resin foam composition is produced. Here, a polyolefin resin, a flame retardant, a foaming agent, and other additives are put into a kneader such as a pressure kneader, a Banbury mixer, a Henschel mixer, or a hot roll, and uniformly dispersed. At this time, it is preferable not to add the respective components at the same time, but to first mix only the resin component at a relatively low speed, and then add the flame retardant, the foaming agent and other additives to uniformly disperse them at a high speed. .. When the resin component and the flame-retardant material and other additives are mixed at the same time, the particles may aggregate to form coarse particles, and coarse bubbles may be formed in the foam.

Next, the composition for a resin foam thus obtained is fed to an extruder with a vent heated to a temperature at which the foaming agent does not decompose, and is molded into a continuous sheet having a constant thickness without bubbles due to air entrainment. And then roll it up. Next, the obtained continuous sheet is subjected to partial crosslinking treatment, if necessary. A radiation crosslinking method can be adopted as the partial crosslinking treatment method. in this case,
Both sides of the continuous sheet are irradiated with ionizing radiation such as electron rays, α rays, β rays and γ rays. The irradiation of radiation is preferably carried out so that the degree of crosslinking of the foam becomes 15 to 60%.

Next, the above continuous sheet is foamed. Here, the continuous sheet is continuously introduced into a foaming furnace heated to a temperature 30 to 100 ° C. higher than the decomposition temperature of the foaming agent. At this time, the continuous sheet is foamed by the decomposition of the foaming agent (including the foaming agent forming the flame-retardant material), and a continuous sheet-shaped foam is obtained. At this time, a film made of the flame retardant that constitutes the flame retardant is formed on the inner surface of the bubbles formed by the foaming agent. As the foaming method, a known method can be applied, and specifically, a vertical hot air foaming method, a horizontal hot air foaming method, a horizontal chemical liquid bath foaming method and the like can be exemplified.

In the above manufacturing method, a chemical crosslinking method may be used together. In this case, a peroxide-based crosslinking agent is added to the flame-retardant resin foam composition in advance. In this case, in the step of foaming the continuous sheet, the foaming by heating and the crosslinking reaction by the crosslinking agent simultaneously proceed. As the cross-linking agent, dicumyl peroxide, tertiary butyl perbenzoate, ditertiary butyl peroxide, etc. are used. These crosslinking agents are preferably added in an amount of 0.5 to 5 parts by weight with respect to the resin component. Flame-retardant resin foam In the flame-retardant resin foam of the present invention obtained by the above-mentioned manufacturing method, the polyolefin resin component is crosslinked. In addition, a film made of the above-mentioned flame retardant is formed on the inner surface of the bubbles. The reason why the film formed by the flame retardant is formed on the inner surface of the bubble is not clear, but it is considered as follows. That is, in the foaming process, bubbles are formed by the decomposition gas of the foaming agent, but at the same time, the dissolved flame retardant adheres to the inside of the bubbles to form a film. Normally, if it is in this state, it is considered that the flame retardant flows out and the coating layer disappears, but since the bubbles are rapidly cooled while being pressurized by the foaming gas, the flame retardant is retained as the coating layer immediately before it flows out. It is thought to be done.

The flame-retardant coating formed on the inner surface of the bubbles can be observed by cutting the foam into thin pieces and magnifying the foam by 5000 to 10000 times using an electron microscope. The thickness of the film formed by the flame retardant is 4 to 6
In the case of μm, it is usually 1 to 2 μm. The flame-retardant resin foam of the present invention preferably has a degree of crosslinking of 15 to 60% and an expansion ratio of 2 to 50. When the degree of cross-linking is less than 15%, the foaming gas is likely to escape during foaming, and it is difficult to achieve a predetermined foaming ratio. Also, the flame retardant coating is less likely to be formed on the inner surface of the bubbles. On the other hand, if it exceeds 60%, the elongation of the foam will be impaired and the moldability will deteriorate. On the other hand, when the expansion ratio is less than 2 times, the cushioning property of the foam is deteriorated. On the contrary, if it exceeds 50 times, it is preferable in terms of flexibility, but the buffering property is deteriorated. Further, the elongation of the foam decreases and the moldability deteriorates.

The above-mentioned degree of crosslinking is a value measured as follows. First, the foam is cut and 0.2 g is precisely weighed. This is immersed in tetralin at 130 ° C. and heated for 3 hours with stirring to take out the molten residue. Then, tetralin is removed from the molten residue with acetone,
Further, pure water is used to remove acetone. The washed molten residue is dried using a hot air dryer at 120 ° C. and naturally cooled to room temperature. The weight W ₁ of the residue at that time is substituted into the following formula (1) to obtain the degree of crosslinking.

[0028]

[Equation 1]

The expansion ratio is a value measured as follows. A 10 × 10 cm test piece is cut out from the foam, and its thickness t ₁ (cm) and weight W ₂ (g) are measured. Then, substituting t ₁ and W ₂ into the following equation (2),
Determine the expansion ratio.

[0030]

[Equation 2]

The foam of the present invention does not exhibit anisotropy in flammability and has uniform flame retardance throughout. It is considered that this is because the flame retardant coating is formed on the inner surface of the foam, so that the flame retardant is spread all over the foam.
Further, at the time of combustion, the coating layer of the flame retardant is melted to cover the combustion part, which is considered to exhibit high flame retardancy. In addition, the foam of the present invention is less likely to spread during combustion if a halogenated phosphorus-containing compound-based flame retardant is used as the flame retardant. It is considered that this is because the phosphorus component contained in the flame retardant promotes carbonization of the foam, solidifies the combustion residue, and suppresses the amount of heat generated during combustion. It is also considered that the halogen contained in the flame retardant dilutes the combustible component generated when the foam is burned.

The foam of the present invention includes, for example, a pipe cover, an air conditioner panel lining material, a heat insulating folded plate formed into a mountain shape by bonding with an iron plate, a cushioning material for automobile interior materials, an engine room partition plate, and an inorganic fiber mat. It can be used in various fields as a composite product such as a laminated non-combustible backing material for a board, a metal plate, a metal foil, a film, an inorganic fiber or the like.

[0033]

EXAMPLES Examples 1 to 5, Comparative Examples 1 to 5 The flame retardant materials shown in Table 1 (Examples) and Table 2 (Comparative Examples) were prepared. And this flame retardant material, Table 3 (Example) and Table 4
The same as the polyolefin resin shown in (Comparative Example)
And decomposition type foaming agents shown in Table 4 and heat stabilizers (Irgan
ox1010: manufactured by Ciba-Geigy Co., Ltd., and a carbon black pigment for coloring were mixed with a Hensyl mixer. The composition obtained was fed to a vented 65 mmφ twin-screw extruder heated to 120 ° C.
400mm wide and 2.2mm thick extruded from the die
Was manufactured.

Next, the obtained long sheet was subjected to a crosslinking / foaming treatment by the crosslinking method and the foaming method shown in Tables 3 and 4. In the case of the electron beam cross-linking method, both sides of the sheet were irradiated with 2.0 Mrad electron beam. In the case of the chemical crosslinking method, 8 parts by weight of dicumyl peroxide was used as a crosslinking agent. In the foaming method, in the case of the chemical solution bath foaming method, a silicone chemical solution bath heated in the order of 210 ° C. → 220 ° C. → 225 ° C. was used. In the case of the vertical hot air foaming method and the horizontal hot air foaming method, heating was performed using hot air heated to 280 ° C. and a radiation heater.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

Evaluation The continuous sheet-shaped flame-retardant resin foams obtained in each Example and each Comparative Example were evaluated as follows. Orientation in the length and width directions The length of the cells of the magic ink of the foam obtained by filling in a 5 x 5 cm grid using a magic ink on a long sheet before foaming and naturally cooling after foaming. Direction (M
The lengths in D _t ) (cm) and width direction (TD _t ) (cm) were measured, and the orientation degrees in the length direction (MD) and the width direction (TD) were calculated by the following formula (3).

[0040]

[Equation 3]

Flame retardance Evaluation according to UL-94 combustion test method (method A) and MVS
Evaluation according to the S302 combustion test method (method B) was performed in the length direction and the width direction of the foam. In the case of UL-94 combustion test method, the quality equivalent to HF-1 was judged to be acceptable. Further, in the case of the MVSS302 combustion test method, a quality equivalent to Class 1 flammability was judged to be acceptable. Mechanical Properties Tensile strength and elongation were measured according to JIS-K6767. Formability Ratio (H / D) of diameter (b) and depth (H) is 0.4
Using a vacuum molding machine equipped with a cup-shaped molding die having a diameter of 5 cm set to 0, 0.50, 0.60, 0.70 and 0.80, the foam is heated to 130 to 180 ° C. and vacuumed. Molded. The ratio (H / D) when the foam could be molded without breaking was taken as the moldability.

The results of each evaluation are shown in Tables 5 and 6.

[0043]

[Table 5]

[0044]

[Table 6]

[0045]

The composition for flame-retardant resin foams according to the first, second, third and fourth aspects of the invention contains the above-mentioned flame-retardant material, and therefore has an anisotropic flame-retardant property. A flame-retardant resin foam having low properties is obtained. According to the flame retardant material according to the fifth, sixth, and seventh aspects, the core particles made of the flame retardant are coated with the foaming agent, so that the resin foam can be imparted with flame retardancy having small anisotropy. .. In particular, in the seventh invention, since the above-mentioned halogenated phosphorus-containing compound-based flame retardant is used, it is possible to realize a flame-retardant resin foam that has low smoke generation and is difficult to spread.

In the flame-retardant resin foam according to the eighth invention,
Since the film made of the flame retardant is formed on the inner surface of the bubble as described above, the flame retardance anisotropy is small. According to the method for producing a flame-retardant resin foam according to the ninth invention, the flame-retardant resin foam according to the eighth invention can be produced.

Claims (9)

[Claims] 1. A flame-retardant resin comprising a polyolefin resin and a flame-retardant material, wherein the flame-retardant material comprises core particles made of a flame retardant and a foaming agent layer coating the core particles. Foam composition. 2. The polyolefin resin has a density of 0.
The flame-retardant resin foam composition according to claim 1, which is a low-density polyethylene resin having a melt flow rate of 910 to 0.930 g / cm ³ and a melt flow rate of 0.5 to 50 g / 10 minutes. 3. The flame-retardant resin foam composition according to claim 2, wherein the low-density polyethylene resin contains less than 90% by weight of another polyolefin resin. 4. The ethylene-propylene copolymer containing ethylene in an amount of 2 to 5% by weight is used as the polyolefin resin.
90% by weight and a density of 0.890 to 0.930 g / cm
50% to 10% by weight of ethylene-α-olefin copolymer of ³
The composition for a flame-retardant resin foam according to claim 1, which comprises: 5. A flame-retardant material comprising core particles made of a flame retardant and a foaming agent layer coating the core particles. 6. The flame retardant material according to claim 5, wherein the flame retardant has a melting point, a softening point or a glass transition temperature of 150 to 250 ° C. 7. The flame retardant is a halogenated phosphorus-containing compound-based flame retardant, and the total amount of phosphorus and halogen is 30 to 80.
The flame-retardant material according to claim (5) or (6), wherein the flame-retardant material is contained by weight. 8. A flame-retardant resin foam, wherein a coating film made of a polyolefin resin and substantially made of a flame retardant is formed on the inner surface of cells. 9. A step of molding a flame-retardant resin foam composition comprising a polyolefin resin and a flame-retardant material in which core particles made of a flame retardant are coated with a foaming agent, and the molded flame-retardant material. A method for producing a flame-retardant resin foam, which comprises a step of heating a composition for a resin foam to crosslink and foam the composition.