JPH04272939A - Foamable resin composition - Google Patents

Abstract

PURPOSE:To prepare the title compsn. which gives a light-wt. molded article having a fine and homogeneous cell structure without detriment to the physical properties. CONSTITUTION:The title compsn. comprises 100 pts.wt. thermoplastic resin contg. 40wt.% or lower ash having a specific surface area of 9X10<3>cm<2>/g or higher and 0.05-1.0 pt.wt. chemical blowing agent, and can be molded into a foamed article having a high foaming ratio and a high bending modulus.

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 foamed articles.

0002

[Prior Art] Conventionally, foaming resin compositions have been widely used because they can be lightweight and cost-reduced, and various foaming agents for injection molding have been commercially available and are added to various thermoplastic resins. Foam molding is possible. By the way, when foaming resin compositions are injection molded at high temperatures, foaming becomes easier, but the effects of heat are greater, resulting in a decline in the physical properties of the molded product and poor appearance, and the biggest problem is that it causes large distortions and warpage. Become. Therefore, there is a need for a resin composition that can be foam-molded at low temperatures. For this purpose, compositions that are foamed using chemical foaming agents are known. For example, JP-A-2-120334
The publication describes a soft foam resin composition for injection molding containing 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 is disclosed in which 0.2 to 3 parts by weight of a chemical blowing agent is added to a resin composition consisting of the following, based on a total of 100 parts by weight of the above composition.

However, these foam molding resin compositions
Although there have been proposals for improving moldability, appearance, and flexibility, there have been almost no proposals for improving mechanical strength. In foam molded products, it is necessary that the air bubbles are uniformly dispersed in microscopic scales in order to achieve a uniform foaming state. In particular, if the bubbles are large, stress concentration occurs there, causing microcrazes and deterioration of physical properties. This is similar to the case where a particulate filler is dispersed in a resin, and it is presumed that stress is concentrated at the interface of the dispersed particles. For this reason, when a foam molded product is made lighter by increasing its foaming rate, the rigidity of the molded product tends to decrease. Therefore, foam molded products are of limited use in structural parts such as automobile parts and electrical parts, and are hardly ever used.

0004

[Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and provides injection molding that can be used as structural parts while suppressing deterioration of physical properties and minimizing deterioration of appearance quality such as warpage and deformation. The purpose is to create a foaming resin composition for use in

[0005]

[Means for Solving the Problems] The foaming resin composition of the present invention is a chemically foamed resin composition based on 100 parts by weight of a thermoplastic resin containing 40% by weight or less of combustion ash having a specific surface area of 9 x 103 cm3/g or more. It is characterized by containing 0.05 to 1.0 parts by weight of the agent. The specific surface area of combustion ash is 9×103
A porous material with a pore size of cm3/g or more is used. When the specific surface area of the combustion ash is less than 9 x 103 cm3/g,
This is not preferable because the adhesion with the resin decreases and the physical properties of the foamed molded product decrease. The particle size of combustion ash is 1 to 1 in terms of weight average particle size.
A thickness in the range of 20 μm is preferable because it has good dispersibility in the foamed molded product and easily contributes to improving the physical properties. The amount added is 4
The filling amount shall be 0% by weight or less. If the amount added exceeds 40% by weight, the resin component will decrease and foaming will become difficult, which is not preferable. Furthermore, a part of this combustion ash can also be used in combination with other fillers such as mica and talc. When other fillers are used together with combustion ash, they can be added in an amount that does not exceed the amount of combustion ash added. If the amount of filler added exceeds the amount of combustion ash, the effect of adding combustion ash will disappear and the disadvantages of using only filler will appear, which is not preferable. That is, the closed cells of the foamed molded product become large, which causes stress to concentrate on the bubbles and causes microcrazes, which is undesirable and causes deterioration of physical properties.

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

The chemical blowing agent is preferably added in an amount of 0.05 to 1.0 parts by weight per 100 parts by weight of the thermoplastic resin. If the amount is less than 0.05 part by weight, resin foaming will hardly be possible, which is not preferable. On the other hand, if it is added in an amount exceeding 1.0 parts by weight, not only will the expansion ratio not increase, but the molded product will foam after molding, making it impossible to maintain dimensional stability, resulting in deterioration of physical properties and cracking, which is not preferable.

[0008] Furthermore, it is preferable that the chemical blowing agent be prepared in the form of a masterbatch using the same type of resin as the resin to be blended, since this facilitates dispersion and handling in the hopper during molding. In this case, the amount of masterbatch used is determined depending on 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, inorganic systems include sodium bicarbonate, ammonium carbonate, ammonium nitrite, sodium borohydride, and the like. Examples of organic compounds include azide compounds such as azodicarbonamide, azobisformamide, isobutyronitrile, and diazoaminobenzene, and nitroso compounds such as N,N'-dinitrosopentamethylenetetramine and N,N'-dinitroterephthalamide. can be mentioned. Furthermore, as a decomposition aid for these blowing agents, generally known inorganic zinc stearate, zinc acetate, organic glycerin, diethylene glycol, etc., and mixed systems may be used. Further, a mixed system of organic and inorganic blowing agents may be used.

[0009] To form this composition, for example, the combustion ash may be mixed with a thermoplastic resin using a conventional mixer, to which a chemical blowing agent may be added, or the three may be mixed together. It's okay. For example, they are mixed and molded using an extruder or mixer. The composition includes antioxidants, lubricants,
Colorants, ultraviolet absorbers, antistatic agents, dispersants, etc. can also be added.

0010

Effects and Effects of the Invention This foamed resin composition contains a specific amount of combustion ash having specific properties as a filler. This combustion ash is uniformly dispersed in the resin matrix layer and reinforces the resin layer. For this reason, in a foamed molded product, the resin matrix layer is uniform, so the bubbles do not become large and can be uniformly dispersed.

[0011] In conventional foam molded articles containing fillers, the adhesion between the resin and the filler is poor, so voids are likely to form at the interface between the resin and the filler. Therefore, foaming pressure is applied all at once to the void interface, generating large bubble cells, resulting in a significant decrease in rigidity such as flexural modulus. However, the combustion ash of the present invention is porous and has good adhesion to the resin, so there are no large voids as described above. In addition, many small bubbles are uniformly dispersed, increasing the foaming rate and suppressing deterioration of the physical properties of the foam molded product.

[0012] As a result, a foam injection molded product can be obtained which can be used as a structural part in automobiles and the like because it is lightweight and exhibits high rigidity.

[0013]

[Examples] Hereinafter, the present invention will be explained in detail using examples. Polypropylene resin (product name J-200) is used as a thermoplastic resin.
3G, manufactured by Idemitsu Petrochemical Co., Ltd.) to 85 parts by weight, a specific surface area of 1.3 x 104 cm3/g and an average particle size of 4.9μ
1.5 parts by weight of a chemical blowing agent was added to a mixture with 15 parts by weight of combustion ash whose composition is shown in Table 1. The foamed resin composition was prepared as No. 1 foamed resin composition. Polypropylene resin 80 weight

[0014]

[Table 1] 1.5 parts by weight of a chemical blowing agent was added to a mixture of 15 parts by weight of combustion ash and 5 parts by weight of mica. A foamed resin composition of No. 2 was prepared. For comparison, No. 1 was prepared by adding 1.5 parts by weight of a chemical blowing agent to a mixture of 80 parts by weight of polypropylene resin and 20 parts by weight of talc, a known filler instead of combustion ash. 3
A foamed resin composition was prepared. However, polysrene EE-205(6) (manufactured by Eiwa Kasei Co., Ltd.) was used as the chemical blowing agent. This is a 10% by weight masterbatch using LDPE as a carrier resin and has a decomposition temperature of 160-220°C. These three types of resin compositions were injection molded at different resin temperatures and their foaming rates were examined.

[0015] Foaming rate=1-(weight of molded product after foaming)/
(Weight of molded product without foaming). Table 2 shows the specific gravity of the molded product obtained. To measure this specific gravity, cut out a test piece from the molded product molded at the above temperature, and
Measured based on STM-D792. The foaming rate was calculated based on this specific gravity. Figure 1 shows a graph of the relationship between molding temperature and foaming rate. No. containing no combustion ash. 3 has a low foaming rate. On the other hand, No. 1 using combustion ash. Nos. 1 and 2 have a high foaming rate, indicating good foamability.

Furthermore, the bending elastic modulus of the above molded article is (A
(Based on STM-D790)

[0017]

[Table 2] The relationship with foaming rate is shown in the line graph of FIG. No. containing no combustion ash. No.3 compared to No.3. 1 and 2 indicate that the elastic modulus is significantly improved. That is, when combustion ash is included, the foaming rate increases and the physical properties are also improved compared to those using conventional fillers. No. 2
This shows that both the foaming rate and physical properties are improved by adding mica to the combustion ash.

[0018] Also, in Fig. 3, No. 1 and no. 3 at 210℃
This is a schematic diagram of a 2 mm thick cross section of a molded product injection molded in 8 times enlarged. No. In No. 3 (b), in which talc was used as the filler, large air bubbles were present;
In case 1 (a) containing combustion ash, the combustion ash has good dispersibility in the resin, so the bubbles do not become large, and the small bubbles are spread uniformly, so it is presumed that there is little decrease in mechanical strength. Ru.

[Brief explanation of the drawing]

FIG. 1 is a graph of the relationship between foam molding resin temperature and foaming rate.

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

FIG. 3 is a schematic diagram showing the state of bubbles in a foamed molded product.

Claims (1)

[Claims] [Claim 1] Specific surface area is 9×103 cm3/g
Thermoplastic resin 100 containing 40% by weight or less of combustion ash of
A foaming resin composition comprising 0.05 to 1.0 parts by weight of a chemical foaming agent.