JP2589222B2 - Foaming resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foaming resin composition used for molding a foamed molded article.

[0002]

2. Description of the Related Art Conventionally, foaming resin compositions have been widely used because they can be reduced in weight and cost, and various foaming agents for injection molding are marketed and added to various thermoplastic resins. Foam molding is possible. By the way, when the foaming resin composition is injection-molded at a high temperature, foaming is easily performed, but the influence of heat is increased, and the physical properties of the molded article are deteriorated, poor appearance is likely to occur, and the biggest problem is large distortion and warpage. Become.
For this reason, a resin composition that can be foam-molded at a low temperature is required. For this purpose, compositions which are foamed using a chemical foaming agent are known. For example, JP-A-2-120334
In the publication, as a soft foamed resin composition for injection molding, 40 to 70% by weight of a thermoplastic block copolymer, 10 to 40% by weight of a polyolefin resin, and 5 to 25% by weight of a rubber softener.
A composition in which 0.2 to 3 parts by weight of a chemical foaming agent is added to the resin composition of

However, these resin compositions for foam molding are:
Although there are proposals for improvement in moldability, appearance, and flexibility, there is almost no proposal for improvement in reduction in mechanical strength. In a foam molded article, it is necessary that air bubbles are microscopically and uniformly dispersed in order to make the foaming state uniform. In particular, when bubbles are large, stress concentration occurs there, and microcrazing occurs to cause deterioration in physical properties. This is the same as the case where the particulate filler is dispersed in the resin, and is presumed to be the same as the concentration of stress at the dispersed particle interface. For this reason, in the case of a foam molded article, when the foaming rate is increased to reduce the weight, the rigidity of the molded article tends to decrease. Therefore, the use of the foam molded article is limited to structural parts such as automobile parts and electric parts, and is hardly used.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is intended to suppress the deterioration of physical properties, suppress the deterioration of appearance such as warpage and deformation as much as possible, and use injection molding which can be used as a structural part. The purpose is to make a foaming resin composition for use.

[0005] The foaming resin composition of the present invention comprises a combustion ash having a specific surface area of at least 9 × 10 ³ cm ² / g in an amount of 15% by weight or more.
With respect to 100 parts by weight of the thermoplastic resin containing 0% by weight or less,
It is characterized by comprising 0.05 to 1.0 parts by weight of a chemical foaming agent. The combustion ash has a specific surface area of 9 × 10 ³ cm ² /
g or more porous material is used. If the specific surface area of the combustion ash is less than 9 × 10 ³ cm ² / g, it is not preferable because the adhesion to the resin is reduced and the physical properties of the foamed molded product are reduced. The particle size of the combustion ash is preferably in the range of 1 to 20 μm in terms of weight average particle size, since the dispersibility in the foamed molded article is good and it is easy to contribute to the improvement of the physical properties. 15% by weight or more 4
The filling amount is 0% by weight or less. If the amount is small,
If the fat tank is not sufficiently strengthened, and if it exceeds 40% by weight, the resin component is reduced and foaming becomes difficult, which is not preferable. Further, a part of the combustion ash can be used in combination with other fillers such as mica and talc. When another filler is used in combination with the combustion ash, it can be added in a range not exceeding the addition amount of the combustion ash. If the added amount of the filler exceeds the amount of the combustion ash, the effect of the addition of the combustion ash is lost and the drawback of the case of using only the filler is undesirably exhibited. That is, the number of independent cells of the foamed molded article becomes large, so that stress is concentrated on the air bubbles and microcraze is generated to cause deterioration in physical properties, which is not preferable.

[0006] The combustion ash is ash generated when combustibles are burned in a fluidized bed boiler or a pulverized coal boiler. Although the ash composition of the combustion ash depends on the combustible used, it is preferable that the ash is discharged when the combustible containing 10% by weight or more of coal is burned from the viewpoint of ash shape stability. Any thermoplastic resin can be used as long as it can be injection molded. For example, any known resin such as a homopolymer or a copolymer of polyethylene, polypropylene, polystyrene, ABS, AS, nylon, polyester, vinyl chloride and the like can be used.

The chemical foaming agent is preferably added in the range of 0.05 to 1.0 part by weight based on 100 parts by weight of the thermoplastic resin. If the amount is less than 0.05 part by weight, resin foaming can hardly be performed, which is not preferable. On the other hand, if it is added in excess of 1.0 part by weight, not only does the foaming ratio not increase, but the molded article also foams after molding and cannot maintain dimensional stability, causing deterioration in physical properties and causing cracks and the like.

The chemical foaming agent is preferably a masterbatch made of the same kind of resin as the resin to be compounded, because it can be easily dispersed and handled in a hopper during molding. In this case, the amount of the masterbatch used is determined according to the content of the chemical blowing agent. For example, in a masterbatch containing 10 parts by weight, the amount added is in the range of 0.5 to 10 parts by weight. Both organic and inorganic chemical blowing agents can be used. For example, examples of the inorganic type include sodium bicarbonate, ammonium carbonate, ammonium nitrite, sodium borohydride, and the like. Examples of the organic system include azide compounds such as azodicarbonamide, azobisformamide, isobutyronitrile, diazoaminobenzene, and nitroso compounds such as N, N'-dinitrosopentamethylenetetramine, N, N'-dinitroterephthalamide. Is mentioned. Further, as a decomposition aid of these foaming agents, generally known inorganic zinc stearate, zinc acetate, organic glycerin, diethylene glycol and the like and a mixed system may be used. Further, a mixed system of organic and inorganic foaming agents may be used.

To form this composition, for example, the combustion ash is mixed with a thermoplastic resin using a conventional mixer, and a chemical blowing agent is added thereto, or the three are mixed together. You may. For example, it is molded by mixing with an extruder or a mixer. The composition includes an antioxidant, a lubricant,
Coloring agents, ultraviolet absorbers, antistatic agents, dispersants and the like can also be added.

[0010]

The foamed resin composition contains a specific amount of combustion ash having a specific property as a filler. This combustion ash is uniformly dispersed in the resin matrix layer to reinforce the resin layer. For this reason, in the foamed molded article, since the matrix layer of the resin is uniform, bubbles can be uniformly dispersed without becoming large.

In a conventional foamed molded article containing a filler, since the adhesion between the resin and the filler is poor, voids are easily formed at the interface between the resin and the filler. Therefore, the foaming pressure is applied to the interface of the void at once, and large cell cells are generated, so that the rigidity such as flexural modulus is remarkably reduced. However, since the combustion ash of the present invention is porous and has good adhesion to a resin, there is no large void as described above. In addition, many small bubbles are dispersed uniformly and the foaming rate is increased, and a decrease in the physical properties of the foamed molded article can be suppressed.

As a result, a foamed injection molded article which can be reduced in weight and has high rigidity and which can be used as a structural part in automobiles and the like is obtained.

[0013]

The present invention will be specifically described below with reference to examples. Polypropylene resin (trade name J-200) as thermoplastic resin
3G, manufactured by Idemitsu Petrochemical Co., Ltd.) and 15 parts by weight of combustion ash having an average particle size of 4.9 μm having a specific surface area of 1.3 × 10 ⁴ cm ² / g and a composition shown in Table 1. To the mixture, 1.5 parts by weight of a chemical blowing agent was added. This was a foamed resin composition of No. 1. 80 weight of polypropylene resin

[0014]

[Table 1] No. 5 parts by weight of a chemical foaming agent was added to the mixture of This was a foamed resin composition of No. 2. As a comparison, 1.5 parts by weight of a chemical foaming agent was added to a mixture of 80 parts by weight of a polypropylene resin and 20 parts by weight of a known filler, talc, instead of combustion ash.
The foamed resin composition of No. 3 was obtained. However, the chemical foaming agent used was Polyslen EE-205 (6) (manufactured by Eiwa Chemical Co., Ltd.). This is 10% by weight using LDPE as carrier resin.
And a decomposition temperature of 160 to 220 ° C. These three types of resin compositions were injection molded while changing the resin temperature, and the foaming ratio was examined.

Foaming rate = 1- (weight of molded article after foaming) /
(Weight of molded article without foaming). Table 2 shows the specific gravity of the obtained molded body. For the measurement of the specific gravity, a test piece was cut out from a molded product molded at the above temperature, and A
It measured based on STM-D792. The foaming ratio was calculated based on the specific gravity. FIG. 1 is a graph showing the relationship between the molding temperature and the foaming ratio. No. containing no combustion ash No. 3 has a low foaming rate. On the other hand, No. 1 using combustion ash. 1 and 2 show that the foaming ratio is high and the foaming property is good.

Further, the flexural modulus of the above-mentioned molded product is expressed as (A
(Based on STM-D790)

[0017]

[Table 2] The relationship with the foaming ratio is shown by the line graph in FIG. No. containing no combustion ash No. 3 compared to No. 3. 1 and 2 indicate that the elastic modulus is significantly improved. In other words, it shows that when combustion ash is included, the foaming rate is increased, and the physical properties are improved as compared with those of the conventional filler. No. 2
The results show that the addition of mica to the combustion ash of Example 1 improved both the foaming rate and the physical properties.

FIG. 1 and No. 3 at 210 ° C
2 shows a schematic diagram of a cross section of 2 mm in thickness, which is eight times larger than a molded product obtained by injection molding in FIG. No. In the case of using talc as the filler of No. 3 (b), large bubbles are present.
In the case of (a) containing combustion ash (1), it is presumed that the combustion ash has good dispersibility in the resin, so that the bubbles do not become large and are uniformly spread with small bubbles, so that the decrease in mechanical strength is small. You.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the temperature of a foamed resin and the foaming ratio.

FIG. 2 is a graph showing a relationship between a foaming rate and a flexural modulus.

FIG. 3 is a schematic view showing a state of bubbles in a foam molded article.

Claims (1)

(57) [Claims] 1. A chemical foaming agent is added in an amount of from 0.05 to 1: 1 based on 100 parts by weight of a thermoplastic resin containing 15 to 40% by weight of combustion ash having a specific surface area of 9 × 10 ³ cm ² / g or more.
A foaming resin composition comprising 0 parts by weight.