JP2665552B2 - Powder resin composition used for powder molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder resin composition used for powder molding, and more particularly, to a fluid immersion method, an electrostatic coating method,
The present invention relates to a powder resin composition used for powder molding such as a powder spraying method, a powder rotational molding method, and a powder slush molding method.

[0002]

2. Description of the Related Art As a powder molding method using a soft powder material, a powder slash molding method using a soft vinyl chloride resin powder is used for an instrument panel, a console box,
Widely used for the skin of car interior parts such as door trim. This is a soft touch, and can be provided with leather grain and stitches, and has good design properties such as a large degree of freedom in design.

However, in recent years, with the worsening of global environmental problems, vinyl chloride resins are being avoided as materials having a large environmental load. This is often misunderstood,
There are many problems such as the necessity of appropriate facilities for incineration, and the time and effort required for separation to avoid mixing with other materials when recycling materials.

Therefore, one method is disclosed in Japanese Patent Laid-Open No. 5-50 / 1993.
No. 50 proposes to use a mixture of a polypropylene resin and an ethylene propylene rubber to which a process oil is added, that is, a freeze-ground powder of an olefin-based thermoplastic elastomer (hereinafter, referred to as TPO).

[0005]

The powder slush molding method which does not apply pressure requires a material having good melt fluidity. However, in general, TPO requires fine powder when the rubber component is increased to increase flexibility. In addition, the melt fluidity decreases, and the chemical resistance also decreases due to the presence of the rubber component. For this reason, the TPO material having good powder slush moldability tends to have a small rubber component and become hard. On the other hand, in the invention described in Japanese Patent Application Laid-Open No. 5-5050, this point is considerably improved, but the problem of hardening has not been solved yet. The present invention has been made to solve such problems, and the powder used in powder molding, which is excellent in the melt fluidity required for powder slush molding, especially the powder having high flexibility and chemical resistance, is required. An object is to provide a resin composition.

[0006]

That is, a feature of the present invention is that a polypropylene resin and a styrene content of 20 are used.
It is a powder resin composition used for powder molding, which is obtained by pulverizing a mixture of a styrene-based thermoplastic elastomer having a weight ratio of 70 % or less and a weight ratio of 70/30 to 30/70. Further, the styrene-based thermoplastic elastomer is a styrene resin having a styrene content of 20% by weight or less. Ethylene butylene. Styrene block copolymer, styrene content 2
0% by weight or less of styrene. Ethylene propylene. Styrene block copolymer, and less selected from styrene content 20% by weight of hydrogenated styrene-butadiene rubber
At least one species .

That is, according to the present invention, a polypropylene resin and a specific styrene-based thermoplastic elastomer for imparting flexibility are kneaded together with a stabilizer or the like in a twin-screw extruder or the like, and the pellets are formed. It is a powder obtained by grinding.

The polypropylene resin used in the present invention comprises:
Either a polypropylene homopolymer or a random copolymer with an α-olefin may be used, but a block or random copolymer using ethylene as the α-olefin is particularly preferred from the viewpoint of the flexibility of the molded product. Also,
For use in powder slush molding without pressure, JI is used as an index of melt fluidity of polypropylene resin.
Load 2.16kgf at 230 ° C by SK7210
(Melt flow rate) measured at 20 g / 1
It must be 0 minutes or more.

The styrene-based thermoplastic elastomer is styrene. Ethylene butylene. Styrene block copolymer (SEBS), styrene. Ethylene propylene.
Styrene block copolymer (SEPS), and Ru at least one kind Oh <br/> selected from styrene <br/> emissions content of 20 wt% or less of a hydrogenated styrene-butadiene rubber (hydrogenated SBR). The SEBS is styrene. butadiene. A hydrogenated styrene block copolymer (SBS),
Clayton G series, a product manufactured by Ciel Chemical Co., Ltd .; and Tuftec H series, a product manufactured by Asahi Kasei Corporation. In this SEBS, the strength increases as the styrene content increases, but the flexibility decreases. In addition, the SEB
In the case of S, the styrene hard segment is aggregated by melting at the time of slush molding, and it may be difficult to obtain a smooth sheet-like molded body. Therefore, the styrene content is preferably not more than 20% by weight.

SEPS is styrene. Isoprene. A hydrogenated styrene block copolymer (SIS),
Septon, a product made by Kuraray Co., is representative. SE
As in the case of BS, the styrene content is preferably not more than 20% by weight because the flexibility decreases as the styrene content increases.

Hydrogenated SBR is a block copolymer of SEB, which is obtained by hydrogenating styrene-butadiene rubber in which styrene and butadiene are randomly copolymerized.
Different from S. A typical example is the Dynalon series, a product made by Nippon Synthetic Rubber Co., Ltd.

The styrene thermoplastic elastomer preferably has a large MFR. Mixing ratio of polypropylene resin and styrene-based thermoplastic elastomer (polypropylene resin / styrene-based thermoplastic elastomer)
Is 70/30 to 30/70 by weight, and 70/30 by weight.
If it exceeds 30, the flexibility is impaired, while the weight ratio is 30/7.
If it is less than 0, the heat resistance and chemical resistance of the molded body will decrease.
The melt fluidity of a mixed system of a polypropylene resin and a styrene-based thermoplastic elastomer is determined by MFR (230 °, 2.16).
At least 8 g / 10 minutes or more in kgf) is required. If it is less than this, a large number of pinholes may remain between the powders of the obtained sheet-shaped molded product, or in an extreme case, the fusion between the powders may be insufficient and the sheet may not be formed.

As a heat stabilizer for a mixture of a polypropylene resin and a styrene-based thermoplastic elastomer, those used for ordinary polyolefins can be used. Generally, a hindered phenol and an organic sulfur-based antioxidant are used in combination, but are not particularly limited.
In addition, a benzothiazole-based light stabilizer may be used as the light stabilizer. Organic and inorganic pigments suitable for ordinary olefins are used. Further, a lubricant such as a fatty acid metal salt and a filler such as calcium carbonate and talc are added as required.

[0014] The mixture of these compounds is a V-blender,
This is performed using a tumbler, Henschel mixer or the like.
Next, the mixture is melt-kneaded by a twin-screw extruder or the like and pelletized. These pellets are finely pulverized using an impact type fine pulverizer such as a turbo mill, a pin mill, and a hammer mill. At this time, it is usually frozen and pulverized using liquid nitrogen. When crushed at room temperature, the yarn is pulled and only a coarse powder is obtained. However, pellets containing less polypropylene resin may be pulverized at room temperature in some cases. The pulverized particles having a particle size of at least 500 μm or less, preferably 300 μm or less are collected by sieving or the like, and those having a particle size exceeding 500 μm are pulverized again.

In the case where the powder resin composition used for powder molding obtained as described above does not have sufficient powder fluidity, the sheet having defects or pinholes without flowing into the complicated shape portion of the mold is used. Will be molded. Therefore, in the present invention, in particular, a filler such as calcium carbonate or silica as a fluidity improver, or a lubricant such as a fatty acid metal salt such as zinc stearate or calcium stearate, a fatty acid amide, or a fatty acid ester in the powder resin composition. Alternatively, at least one resin fine powder or the like can be added. still,
The filler remains without being melted during powder slush molding, but the lubricant and the resin fine powder are melted and taken into the powdered resin composition. These fluidity improvers are added by a mixer such as a Henschel mixer after crushing the pellets, but may be crushed by crushing the pellets before crushing.

Since these additives adhere to the surface of the powder resin composition and act as rollers, there is an effect that the fluidity of the powder can be improved. However, if the above-mentioned additives are added in a large amount, the mechanical properties of the sheet molded body are reduced. Therefore, the amount of the filler and the lubricant is 2 parts per 100 parts by weight of the mixture of the polypropylene resin and the styrene-based thermoplastic elastomer.
Less than 10 parts by weight of the resin fine powder. The resin fine powder is an olefin-based resin having excellent compatibility with the powdered resin composition, and particularly suitable is a low-density polyethylene chemical pulverized product. Chemical pulverization involves dissolving a resin in a solvent and introducing the resin into an insoluble solvent to precipitate the resin. Finer particles can be obtained than in mechanical pulverization.

Next, powder slush molding is performed using the powdered resin composition having the adjusted fluidity. In this molding, the powdered resin composition is dropped into a mold heated above the melting point of the powdered resin composition mainly by gravity, and after a certain period of time, the mold is inverted and excess powdered resin composition is collected in a collection box. The powder resin composition adheres as a layer to the mold surface, and melts over time to form a skin layer. Then, the mold is cooled to remove the skin layer, and this is repeatedly performed.

[0018]

Next, the present invention will be described in more detail with reference to specific examples. Example 1 As a polypropylene resin, Hypol J740 (a polypropylene block copolymer manufactured by Mitsui Petrochemical Co., Ltd., MFR
25 g / 10 min), 50 parts by weight of Clayton G1657 (manufactured by Shell Chemical Company, styrene content 13% by weight, MFR 9 g / 10 min) as SEBS, and Sumilizer GA80 (manufactured by Sumitomo Chemical Co., Ltd., high molecular weight) as a heat stabilizer Hindered phenol) 0.1 parts by weight and Sumilizer T
PD (Sumitomo Chemical Co., Ltd., organic sulfur-based secondary antioxidant)
0.2 parts by weight and Sumisorb 300 as an ultraviolet absorber
0.1 parts by weight (manufactured by Sumitomo Chemical Co., Ltd., benzotriazole) are mixed with a tumbler, and a twin-screw extruder (manufactured by Ikegai Steel Co.
It was extruded at 220 ° C. into a pellet using CM45).

Next, the pellets immersed in liquid nitrogen were put into a Turbomill T250-4J (manufactured by Turbo Kogyo Co., Ltd.) and pulverized to collect only a 500 μm sieve. 1.5 parts by weight of zinc stearate as a fluidity improver was further added to the obtained powder to obtain a powdery resin composition having improved fluidity.

Next, powder slush molding was performed using the above powdered resin composition. As a method of the powder slush molding, first, an electroforming mold (150 mm × 150 mm × 2 m
m) was preheated in an oven heated to 290 ° C., and was taken out of the oven, and when the mold temperature reached 250 ° C., 300 g of the powdered resin composition was dropped at one time to cover the mold surface. After standing for 10 seconds, the mold was inverted to remove excess powder, the mold was returned to the oven and cured for 60 seconds, then the mold was taken out of the oven, quenched, quenched, and the sheet was released. . The thickness of the sheet was about 1 mm.

The pellets and sheets were evaluated for MFR, hardness, tensile strength, elongation and chemical resistance by the following methods.
Table 1 shows the obtained results. In addition, MFR puts the pellet in J
It was measured at 230 ° C. under a load of 2.16 kgf according to IS K7210. The hardness was measured by a JISA hardness tester by stacking six sheets obtained by slush molding. For the tensile strength and elongation, the sheet obtained by slush molding was punched out with a JIS No. 3 dumbbell, and the tensile speed was 200 mm.
/ Min. For chemical resistance, lightly apply gasoline, light oil, engine oil, gear oil, torque converter oil, grease, and kerosene impregnated with gauze to the surface of the sheet obtained by slush molding, and check for abnormalities such as gloss and stickiness. It was confirmed.

Comparative Example 1 A powder resin composition was prepared in the same manner as in Example 1 except that Clayton G1650 (manufactured by Shell Chemical Company, styrene content 29% by weight, MFR 0 g / 10 min) was used as SEBS, and its evaluation was performed. went. Table 1 shows the results.

Example 2 A powder resin composition was prepared and evaluated in the same manner as in Example 1 except that Tuftec H1052 (manufactured by Asahi Kasei Corporation, styrene content: 20% by weight, MFR: 12 g / 10 min) was used as SEBS. Was. Table 1 shows the results.

Comparative Example 2 A powdered resin composition was prepared and evaluated in the same manner as in Example 1 except that Tuftec H1031 (manufactured by Asahi Kasei Corporation, styrene content: 30% by weight, MFR: 160 g / 10 min) was used as SEBS. Was. Table 1 shows the results.

Example 3 Septon 206 as a styrene-based thermoplastic elastomer
3 (Kuraray SEPS, styrene content 13% by weight,
A powder resin composition was prepared and evaluated in the same manner as in Example 1 except that MFR (7 g / 10 min) was used. Table 1 shows the results.

Comparative Example 3 Septon 2002 (SEP manufactured by Kuraray Co., Ltd.) was used as SEPS.
S, styrene content 30% by weight, MFR 65 g / 10 min)
A powdered resin composition was prepared and evaluated in the same manner as in Example 3, except for using. Table 1 shows the results.

Example 4 Dynalon 13 as a styrene-based thermoplastic elastomer
A powdered resin composition was prepared and evaluated in the same manner as in Example 1 except that 20P (hydrogenated SBR manufactured by Nippon Synthetic Rubber Co., styrene content 10% by weight, MFR 4 g / 10 minutes) was used. Table 1 shows the results.

Comparative Example 4 Dynaron 1910P (manufactured by Nippon Synthetic Rubber Co., Ltd., styrene content 30% by weight, MFR 5 g / 10
A powder resin composition was prepared and evaluated in the same manner as in Example 1 except that the above-described Example 1 was used. Table 1 shows the results.

Comparative Example 5 A powder resin composition was prepared and evaluated in the same manner as in Example 1 except that 75% by weight (25% by weight of polypropylene resin) of Kraton G1657, which was SEBS, was used. Table 1 shows the results.

Comparative Example 6 A powdered resin composition was prepared and evaluated in the same manner as in Example 1, except that 25% by weight (75% by weight of polypropylene resin) of Kraton G1657, which was SEBS, was used. Table 1 shows the results.

[0031]

[Table 1]

From these results, in this example, the melt flowability of the powder resin composition is good, and the sheet obtained by slush molding is also rich in flexibility, and has good tensile strength, elongation and chemical resistance. You can see that.

[0033]

As described above, the powder resin composition of the present invention is a material having good melt fluidity and suitable for powder molding.
In addition, a sheet formed by powder molding using this material also has the effect of being rich in flexibility and having good tensile strength, elongation and chemical resistance.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C08K 5/10 KEQ C08K 5/10 KEQ 5/20 KEW 5/20 KEW C08L 9/06 LBG C08L 9 / 06 LBG 53/02 LLY 53/02 LLY // B29K 25:00 (72) Inventor Junichi Kamoto 4-1-1-21 Hamazoedori, Nagata-ku, Kobe Mitsuboshi Belting Co., Ltd. (72) Inventor Seiji Saka Examiner, Mitsuboshi Belting Co., Ltd., 4-1-1, Hamazoe-dori, Nagata-ku, Kobe City Soichi Yushina (56) References JP-A-6-329954 (JP, A) JP-A-6-287365 (JP, A) JP-A-6-192504 (JP, A)

Claims (4)

(57) [Claims] 1. A polypropylene resin having a styrene content of 2
A powder resin composition for use in powder molding, which is obtained by pulverizing a mixture of 0% by weight or less of a styrene-based thermoplastic elastomer at a weight ratio of 70/30 to 30/70. Stuff. 2. A styrene-based thermoplastic elastomer having a styrene content of 20% by weight or less. Ethylene butylene. Styrene block copolymer, styrene having a styrene content of 20% by weight or less. Ethylene propylene. At least one selected from a styrene block copolymer and a hydrogenated styrene butadiene rubber having a styrene content of 20% by weight or less.
The powder resin composition for use in powder molding according to claim 1, which is one kind . 3. The powder molding according to claim 1, wherein the polypropylene resin and the styrene-based thermoplastic elastomer are kneaded by a twin-screw extruder or the like to form a pellet, and the pellet is obtained by cooling or pulverizing the pellet at room temperature. Powder resin composition used for 4. At least one fluidity improver selected from calcium carbonate, silica, metal salts of fatty acids such as zinc stearate and calcium stearate, fatty acid amides, fatty acid esters, and fine resin powders is added. A powder resin composition for use in powder molding according to claim 1.