JPH0341163A - Thermoplastic resin composition - Google Patents

Abstract

PURPOSE:To provide a thermoplastic resin composition which excels in flame retardancy and does not react acidic by mixing thermally expansible graphite, coated with a mixture of an alkaline earth metal compound or the like with a film-forming resin material in a specified ratio, with a thermoplastic resin. CONSTITUTION:Thermally expansible graphite is produced by, for example, a process comprising bringing graphite into contact with a mixture of concentrated sulfuric acid with hydrogen peroxide water, washing the powder with water, and drying the washed graphite. The obtained graphite is coated with a coating composition containing 0.1-50wt.% alkaline earth metal compound (e.g. calcium carbonate) or metal hydroxide (e.g. aluminum hydroxide) and 0.01-5wt.% film-forming resin material (e.g. acrylonitrile/butadiene copolymer). By mixing the coated graphite with a thermoplastic resin (e.g. polyethylene), a thermoplastic resin composition which does not react acidic in spite of the thermally expansible graphite contained and has very high flame retardancy can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermoplastic resin with improved flame retardancy. The composition of the invention is used in the field of plastic molding.

[Prior art] Thermoplastic resins, especially general-purpose resin products such as polyethylene, polypropylene, polystyrene, and polyvinyl chloride,
Although they are produced and used in extremely large quantities for daily necessities, toys, electrical appliances, construction materials, etc., they melt at high temperatures and easily burn when exposed to flames, so various methods have been developed. It has been treated with flame retardant treatment. Widely used flame retardant methods include methods of incorporating halogen compounds, halogenated phosphate ester compounds, metal hydroxides, metal oxides, antimony dioxide, etc. into resins.

Another means of achieving this goal is described in US Pat. No. 3,574,644 by adding thermally expandable graphite to polyethylene! Methods of increasing flammability have been proposed.

However, thermoplastic resin compositions containing thermally expandable graphite obtained by conventionally known methods not only do not necessarily have good flame retardancy, but also have a high flame retardancy when kneading the thermally expandable graphite. Problems such as the generation of acidic gas, which is believed to be mainly composed of sulfuric acid, may corrode the equipment.

[Problem to be solved by the invention]

An object of the present invention is to provide a thermoplastic resin composition that does not generate harmful acid gas when thermally expandable graphite is added to a thermoplastic resin and kneaded, and has excellent flame retardancy.

[Means to solve the problem]

In order to solve the above problems, the present inventors conducted extensive studies and found that the above problems could be solved by incorporating improved thermally expandable graphite that had undergone a specific treatment into a thermoplastic resin. . That is, the present invention is coated with (A) an alkaline earth metal compound or metal hydroxide and (B) a film-forming resinous substance, and the content of (A) is 0.1.
The thermoplastic resin composition is characterized by containing thermally expandable graphite having a content of (B) of 0.01 to 5% by weight and a content of (B) of 0.01 to 5% by weight. The present invention will be explained in detail below.

(Structure of the Invention) The raw material graphite for the thermally expandable graphite used in the present invention is not particularly limited, and natural graphite, pyrolytic graphite, Kinsch graphite, etc. that are used in the production of normal thermally expandable graphite can be used. The thermally expandable graphite used in the present invention can be prepared by contacting raw graphite in a mixture of 98% concentrated sulfuric acid and 60% hydrogen peroxide for 10 to 30 minutes at 45°C or below, and then exposing it to acid. It is produced by washing the treated graphite with water, filtering it, drying it, and then coating it with an alkaline earth metal compound or metal hydroxide and a film-forming resinous substance.

The thermally expandable graphite used in the present invention desirably has an expansion degree of 50 to 250 mn/g when rapidly heated at 1000°C for 10 seconds from the viewpoint of exhibiting a flame retardant effect.

The "degree of expansion" in the present invention refers to 150mj heated in an electric furnace maintained at io o o'c for more than IO minutes! Take out the quartz bead outside the furnace, immediately add 0.5g of thermally expandable graphite, quickly put it into the same furnace maintained at <10oo'c, hold it there for 10 seconds, take it out of the furnace, and let it cool naturally. This is the volume/weight ratio (unit: m427g) of expanded graphite after cooling.

In addition, the particle size of thermally expandable graphite before coating treatment is 20 to 15
It is preferable that the material has 0 mesh, and most preferably that it is classified into about 30 to 100 meshes.

The thermally expandable graphite used in the present invention is prepared by treating raw graphite with an acid as described above, and then adding one or more basic compounds selected from ammonia, aliphatic lower amines, alkali metal compounds, and alkaline earth metal compounds. [Sulfuric acid may be neutralized.

Neutralization treatment is carried out by treating the raw graphite with acid, and then mixing and contacting it with ammonia water, caustic soda aqueous solution, etc. after or during the water washing process. ρI] is preferably about 4.5 to 10.

Alkaline earth metal compounds that coat thermally expandable graphite include calcium, magnesium, and barium hydroxides;
Oxides, carbonates, specific examples include calcium carbonate, calcium oxide, calcium hydroxide, magnesium carbonate,
Magnesium oxide, magnesium hydroxide, barium carbonate, barium oxide, barium hydroxide, etc. are mentioned, and among them, calcium carbonate, calcium hydroxide, magnesium carbonate, and magnesium oxide are preferred. Moreover, aluminum hydroxide is preferable as the metal hydroxide.

Film-forming resinous substances include synthetic polymeric substances such as acrylonitrile-butadiene copolymers, styrene-butadiene copolymers, ethylene-vinyl acetate copolymers,
Examples include polyvinyl acetate resin, polyvinyl chloride resin, polyacrylate resin, and mixtures thereof.These resins may have a part of the monomer chemically modified for modification, or may have a second or third component. It may be copolymerized or additives such as plasticizers may be added. Among these, acrylonitrile-butadiene copolymer with an acrylonitrile content of 15 to 50%, and a styrene content of 20 to 50%.
A styrene-butadiene copolymer having a content of 30% by weight and an ethylene-vinyl acetate copolymer having a vinyl acetate content of 20 to 80% by weight are preferred.

These polymeric substances are used as emulsified dispersions that are emulsified with anionic or nonionic surfactants, and those having a solid content concentration of 1 to 50% are suitable.

Further examples of film-forming resinous substances include synthetic water-soluble polymer substances or natural water-soluble polymer substances, such as polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylic acid Na.
Salt, carboxymethyl cellulose Na salt, carboxymethyl starch Na salt, alginate Na salt, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, ethyl cellulose, as well as natural products such as milk casein protein, glue, gelatin, mannan, gum arabic, guar gum, and chitin. and water-soluble derivatives thereof, which may be used alone or as a mixture. These water-soluble polymers #IyJ usually have a concentration of 0.5% depending on their solubility.
It is used as an aqueous solution of about 1 to 10%, but it may be alkaline or acidic for the purpose of improving solubility.

Furthermore, the thermally expandable graphite used in the present invention contains 0.1 to 50 fE amount % of an alkaline earth metal compound or metal hydroxide and 0.01 to 5 weight % of a film-forming resinous substance. It is necessary to be present.

The content of alkaline earth metal compound or metal hydroxide is 0.
If the content is less than 1% by weight, the effect of suppressing the release of acidic gas at high temperatures cannot be obtained, and even if the content exceeds 50% by weight, not only will there be no corresponding improvement in the effect of suppressing the release of acidic gas. If added too often, the properties of the resin may be impaired.

Furthermore, if the content of the film-forming resinous substance is less than 0.01% by weight, sufficient binding force cannot be exhibited, and even if it is added in an amount greater than 5%, the effect as a binder will not increase. .

Examples of the thermoplastic resin used in the present invention include polyolefin resins such as polyethylene, polypropylene, polybutylene, and copolymers of these seven polymers with vinyl acetate and acrylic ester, polyvinyl chloride resins, polystyrene, Styrenic resins such as acrylonitrile-styrene copolymer and acrylonitrile-butadiene-styrene copolymer, polyester resins such as polyethylene terephthalate and polybutylene terephthalate,
Typical examples include amide resins such as nylon, ether resins such as polyoxymethylene, and elastomers such as chlorinated polyethylene, polybutadiene, and polyisoprene. Among these, those having a chemical structure that is difficult to crystallize, a low melting point, a low melt viscosity, and high fluidity expressed by melt flow rate (MFR) etc. are more suitable. Particularly suitable resins include polyethylene, polypropylene, ethylene-propylene copolymers, and ethylene-hinyl acetate copolymers.

The content of thermally expandable graphite in the thermoplastic resin composition of the present invention is preferably 2 to 80% by weight of the thermoplastic resin composition, and if it is less than 2%, flame retardation may be insufficient. Even if it exceeds 80%, depending on the type of resin and the kneading temperature, the fluidity of the resin mixture decreases during the kneading process with the thermoplastic resin, making it difficult to obtain a uniform mixed composition.

In addition, in the thermoplastic resin composition of the present invention, common additives used in ordinary plastic products, namely,
There are no particular restrictions on the addition or blending of antioxidants, antistatic agents, lubricants, crosslinking agents, dyes and pigments, fillers, etc., and conventionally known flame retardants may be added or used in combination.

The method for producing the thermoplastic resin composition of the present invention includes:
The thermoplastic resin and a predetermined amount of thermally expandable graphite are stirred and mixed using a commonly used mixing device such as a Henschel mixer or a ribbon blender, and then kneaded using a commonly used mixing device such as a single or twin screw extruder, kneader, or Banbury mixer. Examples of methods include kneading in a machine, or using two heated rolls and kneading by performing a turning operation.

As for the temperature conditions during kneading, it is advantageous to range from a temperature at least 30°C higher than the melting point of the thermoplastic resin used, to an upper limit of about 250°C as the temperature of the γ11 kneaded mixture.

The kneading time varies depending on the type of kneading device, temperature conditions, and fluidity of the resin, but is usually 2 minutes to 20 minutes. Note that as the temperature of the kneaded mixture approaches 250°C, it is necessary to set the kneading time shorter.

On the other hand, as the temperature decreases, the kneading efficiency tends to decrease and a longer kneading time is required.

Suitable mixing conditions include, for example, 170 to 210°C (mixture temperature) for 3 to 5 minutes in a batch-type kneader, Banbury mixer, etc., and 170 to 220'C in a continuous extrusion screw, etc. (mixture temperature) and the residence time is about 1 to 4 minutes.

The thermoplastic resin composition of the present invention can be generally made into extruded sheets, injection molded products, etc., and can also be made into foam molded products by adding a foaming agent. In addition, the thermoplastic resin composition of the present invention can be made into molded products directly, or can be diluted with other thermoplastic resins as a master haunch or compound, or mixed with other resins to form molded products. good.

In addition, the thermoplastic resin composition produced by the present invention or a molded article using the same may be made into a composite material by combining different materials for the purpose of aestheticizing the surface, making it water resistant, making it flame retardant, etc. It is also possible to manufacture.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof. In addition, in Examples and Comparative Examples, "part" means "part by weight" and "%" means "wt% J
shows.

Examples 1 to 6, Comparative Examples 1 and 2 Thermal expandable graphite and polyethylene (Mitsubishi Chemical Made on the side, "Mitsubishi Polyech HD JSIIOJMFRl, I, d=0.9
52) were kneaded in the blending amounts shown in Table 1 by the kneading method (2) below to obtain a resin composition. In addition, in order to confirm the generation of acid gas during the kneading operation, after 4 minutes of kneading time had elapsed after adding thermally expandable graphite, a PL+ test paper (manufactured by MACHREY-NAGEL, Three Band rTl'? ITEST-L type JpH1-11
) was inserted into the kneading device to measure the pit of the gas phase, and another pH test paper was similarly brought into instant contact with the surface of the mixture to measure the pit of the composition. Results first
Shown in the table.

Furthermore, using the resin composition obtained in this way, test pieces were prepared by the method described in (2) below, and a flammability test was carried out using J.
The oxygen index was measured according to IS-7201.

The results are shown in Table 1.

■ Kneading method Mixing chamber of Brabender Plasticorder J manufactured by Brabender Co., Ltd. Temperature 220" C1 rotation speed 30
rpm, put polyethylene into this chamber, and after it starts to be kneaded in a fluid state, thermally expandable graphite is added over a period of about 15 seconds, and the kneading operation is continued while maintaining the same conditions. continued for 4 minutes.

■ How to prepare a test piece In a heat press machine preset at 200°C,
A metal spacer of nm x 10 nm x 5 iun was installed, and about 7 parts of the mixture after the kneading operation was mixed with 100 nm
kg/cod for 1 minute, and then the pressure was released to obtain a sheet, which was used as a test piece.

The types of thermally expandable graphite, alkaline earth metal compound, metal hydroxide, and film-forming resinous substance used are shown below.

thermally expandable graphite ■Two particle size 36-80 mensch, medium t with NaOH.

Treatment, expansion pressure; 200ml/gr, pH; 7.7
Particle size 36-80 mesh, neutralized with Ca(OH)z, expansion pressure: 195mj2/gr, pH: 7゜■ particle size 36-80 mesh, neutralized with NH3, expansion pressure: 205ml/ g r, pH; 5.4ρ11
is the pH of a 1% by weight aqueous dispersion.

Alkaline earth metal compound or metal hydroxide (abbreviated as metal compound in the table)
)3: Showa Denko's "Hisilite H-31" Mg (OH
) z "High purity water mug 200-6J film-forming resinous substance NBR" manufactured by Asahi Glass: NBR Latex Sox rNippo manufactured by Nippon Zeon ■
l 1571J PVA: Nippon Gohsenol NH manufactured by Nippon Gosei Kagaku Kogyo (In)
-133” water? Yong? Night CMC-Na: “Celogen 3I4” manufactured by Daiichi Kogyo Seiyaku ■
Water of? [Effects of the Invention] The thermoplastic resin composition of the present invention does not exhibit acidity even if it contains thermally expandable graphite, and the thermoplastic resin composition has extremely high flame retardancy.

Further, when this composition is mixed and kneaded with other thermoplastic resins, the mixed composition does not become acidic.

Claims (1)

[Claims] (1) coated with (A) an alkaline earth metal compound or metal hydroxide and (B) a film-forming resinous substance, the content of (A) being 0.1 to 50% by weight, (B) A thermoplastic resin composition comprising thermally expandable graphite having a content of 0.01 to 5% by weight.