JPH0341161A - Production of thermoplastic resin composition - Google Patents

Abstract

PURPOSE:To obtain a thermoplastic resin composition which does not produce any noxious acidic gas during kneading and is improved in flame retardancy by kneading a thermoplastic resin with thermally expansible graphite of a low acidic impurity content below a specified temperature. CONSTITUTION:Thermally expansible graphite of a pH>=4.5 in a 1wt.% aqueous dispersion thereof is prepared by, for example, a process comprising stirring a graphite powder in a mixture of concentrated sulfuric acid with hydrogen peroxide water, washing the powder well with water, optionally neutralizing it with ammonia water or the like, and drying it. A thermoplastic resin composition is obtained by kneading this graphite with a thermoplastic resin (e.g. polyethylene) with, e.g. a Henschel mixer while keeping the temperature of the melt-mixture at 210 deg.C or below. In this way, the melt-mixture does not reacts acidic, and the flame retardancy of the obtained thermoplastic resin composition can be markedly increased.

Description

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

[Prior Art 1 Thermoplastic resins, especially general-purpose resin products such as polyethylene, polypropylene, polystyrene, and polyvinyl chloride, are produced and used in extremely large quantities in the fields of daily necessities, toys, electrical appliances, construction materials, etc. All of them melt at high temperatures and burn easily when exposed to flames, so they are treated with various flame-retardant treatments. ! A method widely used as a combustion method includes a method of incorporating a helodene compound, a halogenated phosphate ester compound, a metal hydroxide, a metal oxide, antimony trioxide, etc. into the resin.

As another means for achieving this objective, US Pat. No. 3,574,644 proposes a method of increasing flame retardancy by adding thermally expandable graphite to polyethylene.

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 1 The present invention provides a thermally expandable graphite that does not generate harmful acid gases when added to a thermoplastic resin and is kneaded, and that has excellent flame retardancy as compared to the frame valve. It is an object of the present invention to provide a method for manufacturing a plastic resin composition.

[Means for Solving Problem 31 1 In order to solve the above problems, the present inventors have made extensive studies and found that by kneading a specific thermally expandable graphite and a thermoplastic resin under specific temperature conditions, We have found a solution to the above problem. That is, the present invention provides thermoplastic resin and 1
Thermal expandable graphite whose pH of the weight% aqueous dispersion is 4.5 or more,
The temperature of the mixed wire mixture of the thermoplastic resin and thermally expandable graphite is 2.
The gist of the present invention is a method for producing a thermoplastic resin composition whose Vf characteristic is kneading while maintaining the temperature at 10° C. or lower.

The present invention will be explained in detail below.

There are no particular restrictions on the raw material graphite and 9I manufacturing method for the thermally expandable graphite used in the present invention, but its characteristics include 1000
The degree of expansion when rapidly heated at ℃ for 10 seconds is 50~2
Desirably, the thermally expandable graphite is pulverized into approximately 20 to 100 meshes in a mixture of 98% concentrated sulfuric acid and 60% hydrogen peroxide. Leave in contact for 10 to 30 minutes at temperatures below ℃, wash with water,
It can be manufactured by drying.

The degree of expansion of thermally expandable graphite generally depends on the particle size of the thermally expandable graphite, and when the particle size is finer than about 80 mesh, the expandability tends to decrease.When the particle size is finer than 150 mesh, the expansion degree is drastically reduced, and as a result,
The flame retardant effect of thermoplastic resin composition products is significantly reduced.

Therefore, the particle size of the thermally expandable graphite used in the present invention is 1
A value larger than 00 mesh is desirable.

On the other hand, those larger than 20 mesh have a large expansion degree,
Although it is effective in imparting flame retardancy, when kneaded with a thermoplastic resin, the dispersibility in the FM resin may decrease.

The particle size of thermally expandable graphite usually depends on the particle size of the raw graphite used to make it, so the particle size may be adjusted using the raw graphite, or the expanded graphite may be crushed and classified. You can go there.

The thermally expandable graphite used in the present invention has a pH of 4.5 or higher, preferably 4.5 to 10 (7% by weight).
) range. If the pH of the 1% by weight aqueous dispersion is less than 4.5, acidic gas will be generated during cross-wire work, and the flame retardance of the resulting thermoplastic resin composition will not be sufficiently improved. 5 or more thermally expandable graphite can also be obtained by repeatedly washing the graphite with water after the above acid treatment to remove excess acid, but after washing with water to some extent,
It can also be obtained by neutralizing with ammonia, aliphatic lower amine, alkali metal compound or alkaline earth metal compound. It is preferable to use neutralized thermally expandable graphite from the viewpoint of improving the flame retardancy of the thermoplastic IM resin or acid and from the viewpoint of wastewater treatment in the glazing process of thermally expandable graphite.

Examples of aliphatic lower amines include monomethylamine, trimethylamine, trinothylamine, ethylamine, propylamine, and butylamine.

Examples of the alkali metal compound and alkaline earth metal compound include compounds selected from hydroxides, oxides, carbonates, sulfates, and organic acid salts of potassium, sodium, calcium, barium, or magnesium.

Among these, preferred specific examples include ammonia, caustic potash, caustic soda, potassium carbonate, soda carbonate, sodium formate, sodium acetate, sodium citrate, calcium hydroxide,
Barium hydroxide, magnesium hydroxide, calcium carbonate, barium carbonate, magnesium carbonate, calcium acetate,
Examples include barium acetate and magnesium acetate, and these compounds can be used alone or in combination of two or more.

These compounds are used in an amount equivalent to neutralizing the free sulfuric acid contained in the graphite after acid treatment, and it is desirable that they form a salt with the free sulfuric acid, but the excess should be contained as a compound. That is, graphite may be treated with an acid, and after or during the water washing process, ammonia, aliphatic lower amine, alkali metal compound, or alkaline earth metal compound may be added as it is or as a mixture with water, If necessary, excess of these compounds is removed and dried to produce thermally expandable graphite.

Examples of the thermoplastic resin used in the present invention include polyethylene, polypropylene, polybutylene, polyvinyl chloride resins, polystyrene, styrene resins such as acrylonitrile-styrene copolymer, acrylonitrile-butanoene-styrene copolymer, Typical resins include polyester resins such as polyethylene terephthalate, 7-amide resins such as nylon, and elastomers such as ene. Among these, those having a chemical structure that is difficult to crystallize, a low melting point, a low melt viscosity, and a high fluidity expressed by melt flow rate (MFR) are more suitable. Particularly suitable υI
The fat is polyolefins, for example, with a density of 0.91.
S~0.935g/-, melting point less than 115'C, JIS
Low-density polyethylene with a melt flow rate of 1 to 100 g/10 in/root flow rate at 190°C as specified in K-6760, 1 to 10
Mention may be made of polypropylene of about 0g/10 in or ethylene-vinyl acetate copolymer with a vinyl acetate content of 10 to 90i31%.

Heat to the thermoplastic resin composition in the present invention! Depending on the type of resin, 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 raw material 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 mixed using a commonly used mixing device such as a single or twin screw extruder, Niegoo mixer, or Banbury mixer. For example, the mixture may be kneaded using a kneading machine that has a treadmill, or a heating double-bar kneader or the like may be used to perform a turning operation.

The temperature conditions for kneading are above the melting point of the thermoplastic resin raw material used, and the temperature of the kneaded mixture is 210"C.
A range with upper limit l! It is 11.

In general, the addition of thermally expandable graphite tends to reduce the fluidity of the mixture compared to the case of resin alone;
It is more advantageous to knead at a temperature higher than 200° C., and it is preferable to set the upper limit temperature to 200° C. or lower since there is a temperature rise due to self-heating during iRMI operation.

The opening time during kneading varies depending on the type of kneading device, temperature conditions, and fluidity of the resin, but is usually 2 minutes to 20 minutes. As the temperature of the crosstalk mixture approaches the upper limit of 210°C, the crosstalk mixture at t1
It is necessary to set n short.

As the power and temperature decrease, the kneading efficiency tends to decrease and a longer mixing time is required.

A suitable mixed thread VF is, for example, FW1 at 170 to 190°C (mixture temperature) for 3 to 5 minutes in a batch system Niegoo, Banbury mixer, etc., and 170 to 200°C (mixture temperature) in a continuous extrusion screw, etc. (temperature) and the boiling time is about 1-4 minutes.

The thermoplastic elf fat composition of the present invention usually comprises an extruded sheet,
In addition to being able to be made into injection molded products, it can also be used as foam molded products by adding a foaming agent. Furthermore, it can be diluted with other thermoplastic resins as a masterbatch or powder, or mixed with other resins to form molded products.

In either case, the content ratio A of thermally expandable graphite is determined as appropriate depending on the degree of flame retardancy required. Needless to say, it can be adjusted.

Furthermore, the thermoplastic resin composition produced according to the present invention or a molded article using the same may be further combined with different materials for the purpose of aestheticizing the surface, making it water resistant, making it flame retardant, etc. It is also possible to produce composite materials.

The present invention will be explained in more detail below using Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof. In the Examples and Comparative Examples, "part" indicates "part by weight" and "%" indicates "% by weight".

Examples 1 to 8, Comparative Examples 1 to 3 Thermal expandable graphite and thermoplastic 131 resin shown in Table 1 were subjected to tI
A thermoplastic resin composition was produced by mixing according to the following mixing method (2) using the blending amounts and V mixing conditions shown in Table S1. At the end of the kneading operation, a water-moistened pi-+ test piece was inserted into the mixer to check the pH of the gas phase, which showed no acidity. Sheets were manufactured using the obtained thermoplastic resin composition according to the sheet forming method described in (1) below, and the oxygen index of these sheets was measured in accordance with JIS-7201 as a flame retardant test. The results are shown in Table 1.

■ Kneading method Set the mixing chamber of "Brabender Plastico Goo" manufactured by Brabender Co., Ltd. to the temperature shown in Table 1, set the rotation speed to 30 rpm, and add the blended amounts shown in Table 1 to this chamber. After the resin began to be kneaded in a fluidized state, thermally expandable graphite in the amount shown in Table 1 was continuously added over a period of about 15 seconds. The same conditions were maintained and the kneading operation was kept open at specified times.

■ Sheeting method: 120 questions x
10 questions x 511111 metal spacers are installed,
Approximately 100 k of the mixture after the cross-talk operation was
g/cl for 1 minute, and then the pressure was released to obtain a sheet.

The types of thermally expandable graphite and thermoplastic resin used are shown below.

Thermally expandable graphite A: Particle size 36-80 mesh, expansion rate 200 ml/glN at 1000°C for 10 seconds Neutralization treatment with H3 B: Particle size 36-80 mesh, expansion rate 200 wl/g at 1000°C for 110 seconds, with NaOH Neutralization treatment C: particle size 36-80/-7, i o o o
'c, degree of expansion for 10 seconds 190 m1/g, neutralization treatment with Ca(OH)2 D: particle size 36-80/-/x, 1000'C
Degree of expansion for 110 seconds 200 theory 1/g5 Thermoplasticity only after washing with water 84N PE: Polyethylene Mitsubishi Polyethylene HD JS 110J manufactured by Mitsubishi Kasei Corporation MFR: 11, d=0.9
52 PP: Polypropylene Mitsubishi Yuka Co., Ltd. V! rz-Bren FY-6J MFR: 2.3, d=0.90EVA:
Ethylene-vinyl acetate copolymer Mikata Polychemical C Co., Ltd.)'J
lr Evaflex 150JM I :30 <g/
10 win), VA33% From the results in Table 1, it is clear that the thermoplastic resin composition obtained by the production method of the present invention exhibits extremely high flame retardancy. Also, the present invention! If the il manufacturing method is used, no acidic gas is generated and the resin composition does not exhibit acidity.

[Effect of the invention 1 According to the present invention, thermoplasticity! (adding thermally expandable graphite to fat,
During kneading, the mixed wire mixture does not exhibit acidity, and the resulting thermoplastic resin composition can have extremely high flame retardancy.

Claims (1)

[Claims] (1) The pH of the thermoplastic resin and the 1% by weight aqueous dispersion is 4.
5 or more of thermally expandable graphite is kneaded while maintaining the temperature of the kneaded mixture of the thermoplastic resin and thermally expandable graphite at 210° C. or lower.