JPS585930B2 - Nannensei Polyolefin Inhatsupoutai Oyobi Sonoseizohouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a closed-cell, high-density polyolefin foam with excellent flame retardancy and a method for producing the same.

In general, polyolefin foams are widely used as heat insulating materials, heat retaining materials, cushioning materials, etc. because they are inexpensive and have excellent properties.

In particular, these materials are often used in the field of building materials, and in such fields, there is a strong demand for materials with excellent flame retardancy.

However, because polyolefin is the most chemically stable due to its molecular structure, it is said to be extremely difficult to make it flame retardant, especially for closed cell foams with high ratios. It has been considered extremely difficult to improve flame retardancy without impairing the properties of

In order to make conventional polyolefin flame retardant,
Traditionally, halogen compounds, chlorinated paraffin, and antimony trioxide were added to polyolefin, or antimony trioxide was added to halogen compounds, but in order to make polyolefin flame retardant with these flame retardants, , the flame retardant is added to the polyolefin from 10 to
The flame retardant must be added in a large amount of 20% or more, and the use of such a large amount of flame retardant significantly inhibits the original properties of the polyolefin, and when the polyolefin is foamed, pores are created in the foam membrane. This causes the bubbles to become continuous,
The foaming ratio and mechanical performance are reduced and the foam cannot fully function as a foam.

The present invention has been made as a result of extensive research aimed at improving these drawbacks, and has resulted in the discovery of a polyolefin foam body and a method for producing the same, which do not impede the foam's function and have excellent flame retardancy.

That is, the present invention is a polyolefin foam obtained by adhering a solid halogen compound flame retardant with a particle size of 5 μm to 50 μm to a cellular membrane, and in order to produce the foam, 100 parts by weight of polyolefin is added with a particle size of 5 μm to 50 μm. A composition containing 3 to 20 parts by weight of a 50 μm solid halogen compound flame retardant and a foaming agent is extruded from an extruder and foamed.

The key point of the present invention is to use halogenated flame retardant particles having a large particle size, and this point is completely different from conventional flame-retardant polyolefins.

That is, conventionally, the particle size of the flame retardant added to polyolefin was made as fine as possible and uniformly dispersed in the polyolefin.

As a result of a detailed study of the prior art, the present inventors found that the method of dispersing a flame retardant in the form of liquid or fine particles into polyolefin is effective when attempting to obtain non-foamed or low-magnification foams. However, it has been found that when a foam with a high expansion ratio (expansion ratio of 5 times or more) is obtained, the foam does not become a closed cell foam.

That is, fine particles of flame retardant are contained in the cell membrane, and the number of particles is extremely large, so that pores are generated in the cell membrane.

In the present invention, by using a flame retardant having a large particle size, the number of particles is minimized, and the flame retardant particles themselves act as the agent for forming bubbles.

To explain this in more detail, conventionally when extruding and foaming a composition in which a flame retardant and a volatile blowing agent were added to polyolefin, the blowing agent was dissolved in the polyolefin under high temperature and high pressure, and this was dissolved in the air. It is thought that when the flame retardant particles are extruded, they aggregate around the flame retardant particles and gasify to form bubbles, but in this case, if a solid halogen flame retardant with a large particle size is used, the flame retardant acts as a nucleating agent. It is presumed that this works effectively and that a foam with a high magnification ratio that does not contain flame retardant particles in the cell membrane can be obtained.

That is, in the present invention, the flame retardant particles are not present inside the cellular membrane or in the intersections of the cellular membranes (referred to as strands), but are attached to the surface of the polyolefin forming the cellular membrane. It exists in a state of being

However, some areas are covered with a thin film of polyolefin.

In any case, the flame retardant is not dispersed in the polyolefin phase.

Note that a plurality of flame retardant particles are usually contained per cell.

Therefore, it is necessary for the flame retardant used in the present invention to maintain its original particle size without melting while being added to the polyolefin and molded. It must have the following characteristics.

Examples of such high melting point solid halogen compound flame retardants include halogenated aromatic compounds such as hexabromobenzene, bentabromotoluene, decabromodiphenyl oxide, octabromobiphenyl, and tetrabromobisphenol A; Further, halogenated alicyclic flame retardants such as perchloropentacyclododecane and hexabromocyclododecane are included.

In addition, in the present invention, the particle size of the halogen compound flame retardant is 5 μm.
The reason for limiting the range to ~50μ is that it is larger than the thickness of the cell membrane of the foam; if it is less than 5μ, the flame retardant will be uniformly dispersed in the olefin, and the bubble nuclei will be This is because if the diameter exceeds 50μ, the bubble diameter becomes coarse and it is not possible to form a foam made of uniformly fine bubble diameters.

Note that the term "uniform, fine bubbles" refers to bubbles that are free of voids and have an average diameter of 1 mm ψ or less, preferably less than 0.5 mm ψ.

The reason why the amount of the flame retardant added is limited to 3 to 20 parts by weight per 100 parts by weight of polyolefin is that if it is less than 3 parts by weight, the flame retardant effect cannot be fully exhibited. This is because if the amount is exceeded, the flame retardant will not only adhere to the cell membrane but also be dispersed in the polyolefin, which will interfere with the intended effects and effects of the present invention.

The amount added is preferably 3 to 10 parts by weight.

As described above, the amount of flame retardant added is the same as in the conventional one, but since the flame retardant is not dispersed in the polyolefin, it does not impede the properties of the polyolefin in any way.

Further, in the present invention, antimony trioxide is often added as a flame retardant aid, and in this case, it is desirable to use antimony trioxide having a particle size of 5 μm to 50 μm, which is the same as that of the flame retardant.

To specifically explain the manufacturing method of the present invention, first, a polyolefin having a melt index of 2.0 or less, such as crystalline polypropylene, high-density polyethylene, low-density polyethylene, or a copolymer mainly composed of ethylene and propylene, is used. While a desired composition consisting of a combination or a mixture thereof and a flame retardant and a flame retardant aid as described above is fed from the hopper of the extruder, a volatile blowing agent is fed from a small hole in the barrel of the extruder. For example, trichlorotrifluoroethane,
While quantitatively injecting halogenated aliphatic hydrocarbons such as monochlorotrifluoromethane, aliphatic hydrocarbons such as butane and pentane, and alcohols such as methanol and ethanol, the mixture is thoroughly mixed and dissolved with the composition. A polyolefin foam is obtained by foaming while extruding from a goo having a desired shape.

The most preferred polyolefin is crystalline polypropylene, which has excellent heat resistance.

In addition, the flame retardant should be added in advance at a ratio of 3 to 1 to the polyolefin.
It is advisable to mix it as a high concentration masterbatch of about 5 times.

Further, commonly used coloring pigments, antioxidants, metal deactivators, ultraviolet absorbers, etc. may be added to the above composition as required.

Next, examples of the present invention will be described.

(The following parts indicate parts by weight.) Example 1 100 parts of commercially available crystalline polypropylene (specific gravity 0.90, melt index 0.3) was added with particles having a particle size of 10μ to 4.
A composition containing 5 parts of decabromodiphenyl oxide having a distribution of 0μ and 3 parts of antimony trioxide having a particle size of 2μ or less was fed into the hopper of a 40 mmψ extruder.

In this case, decapromodeiphenyl oxide and antimony trioxide were kneaded as a masterbatch at a concentration 5 times that of polypropylene, and the mixture was made into pellets.

Meanwhile, 5 parts of trichlorotrifluoroethane was added to 100 parts of polypropylene through a small hole in the barrel of the extruder.
The mixture was injected at a ratio of 4 parts, kneaded, and extruded through a die of an extruder to foam.

The extrusion setting temperature is 200℃ and 200℃ from the hopper side.
, 170°C, 170°C die part 140°C, and rotation speed was 16r. p. It is m.

Immediately after discharge, the extrudate shrank significantly, but the shrinkage was recovered by heat storage in a 100° C. air constant temperature bath for about 1 hour.

The thus obtained foam had a density of 0.02 g/cc and an average cell diameter of 0.52 mmψ on the cut surface.

Furthermore, when the cell membrane of this foam was observed under a microscope, coarse particles of the flame retardant were found to be attached to the surface of the cell membrane.

Although minute particles of antimony trioxide were dispersed in the bubble film, no voids were observed in the bubble film.

Further, flame retardancy was measured by the method of ASTM D1692 and found that it self-disappeared. Comparative Example 1 A foam was obtained in the same manner as in Example 1 except that decabromodiphenyl oxide with a particle size of 4 μm was used.

However, the shrinkage of the foam after being discharged from the extruder was extremely small, the density after heat treatment was 0.02 g/cc, and the average cell diameter on the cut surface was 1.45 mmψ.

Furthermore, when the bubble film was observed, no voids were found in the bubble film.

Example 2 All experiments were carried out except that 6 parts of hexabromobenzene in the form of acicular particles with a major axis distribution of 10μ to 50μ and a breadth of 3μ or less and 3 parts of antimony trioxide with a particle size of 2μ or less were used as flame retardants. A foam was obtained in the same manner as in Example 1.

The density of the obtained foam was 0.02 g/cc, and the average cell diameter at the cut surface was 0.4 mmψ, making it a uniform cell.

Furthermore, the cell membrane had no voids and was a highly elastic, flame-retardant foam with closed cells.

Comparative Example 2 A foam was obtained in the same manner as in Example 1, except that 6 parts of hexabromobenzene with a major diameter of less than 5 μm and 3 parts of antimony trioxide with a particle size of 2 μm or less were used as flame retardants.

The cell diameter of the obtained foam was 1.3 mmψ, and voids were observed in the cell membrane on the cut surface.

As detailed above, the present invention has remarkable effects such as obtaining a flame-retardant polyolefin foam having uniform and fine cell diameters with excellent flame retardancy and no voids in the cell membrane.

Claims (1)

[Scope of Claims] 1. In a crystalline polyolefin high-density foam, a solid halogen compound flame retardant 3 to 100 parts by weight of the crystalline polyolefin has a melting point higher than the melting point of the polyolefin and has a particle size of 5 μ to 50 μ. A flame-retardant polyolefin foam, characterized in that 20 parts by weight of the foam is attached to a cellular membrane. 2 Having a melting point higher than the melting point of the polyolefin and having a particle size of 5μ to 50% by weight based on 100 parts by weight of the crystalline polyolefin.
A method for producing a flame-retardant polyolefin foam, which comprises foaming a composition to which 3 to 20 parts by weight of a solid halogen compound flame retardant and a foaming agent are extruded from an extruder.