JP2853952B2 - Foamable polyolefin resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a foamable polyolefin resin composition.

[0002]

2. Description of the Related Art Polyolefin resin foams are excellent in flexibility and heat insulation, and have been used as interior materials for vehicles such as ceilings, doors and instrument panels. These interior materials are molded by vacuum molding, compression molding, etc., but since the molding temperature is high, a foam obtained by foaming a polyolefin resin containing a polypropylene resin having excellent heat resistance is mainly used. I have been.

[0003] However, polypropylene resins are
Crosslinking, ionizing radiation used at the time of foaming, the molecular chain is easily broken by peroxides and the like, so that a foam obtained by foaming a polyolefin resin containing a polyethylene resin in addition to a polypropylene resin is used. It has become.

[0004] As a method for producing the above-mentioned polyolefin resin foam, for example, Japanese Patent Publication No. 46-37716 and Japanese Patent Application Laid-Open No. 64-87641 disclose a method in which a polyolefin resin sheet is crosslinked with ionizing radiation and then crosslinked. However, none of these methods could prevent deterioration of the uncrosslinked portion.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks, the present invention provides a foam which is hardly deteriorated even when irradiated with ionizing radiation, has excellent heat resistance and moldability, and has excellent adhesion to a skin material. An object of the present invention is to provide a foamable polyolefin-based resin composition from which a body can be obtained.

[0006]

Means for Solving the Problems The resin matrix used in the present invention is a resin matrix composed of a polypropylene resin and a polyethylene resin. The polypropylene resin is a resin containing propylene and an α-olefin other than propylene as constituent units. Examples of the α-olefin other than propylene include ethylene, 1-butene, 1-pentene, 1-hexene,
-Methyl-1 pentene, 1-heptene, 1-octene and the like.

The content of the above-mentioned α-olefin is limited to 2 to 10% by weight in the polypropylene resin, and preferably 2.2, since the moldability of the obtained foam is reduced whether the content is low or high. -8% by weight, more preferably 2.5-6% by weight.

The weight-average molecular weight / number-average molecular weight of the above polypropylene resin is limited to 3 to 7, since the moldability of the obtained foam decreases as the molecular weight decreases and the heat resistance of the obtained foam decreases as the molecular weight increases. , Preferably 3.3 to
6.5, more preferably 3.5-6.

The content of the above polypropylene resin is limited to 40 to 90% by weight in the resin matrix because the heat resistance of the obtained foam is reduced when the content is reduced, and the moldability of the obtained foam is reduced when the content is increased. , Preferably 45
~ 85% by weight.

[0010] The melt index of the polyethylene resin is limited to 2 to 50 g / 10 minutes, because the lower the melt index, the lower the moldability of the obtained foam, and the higher the melt index, the lower the heat resistance of the obtained foam. Is 3 to 3
0 g / 10 min, more preferably 4 to 25 g / 10 min.
Minutes.

Examples of the polyethylene resin include an ethylene homopolymer and a copolymer of ethylene and an α-olefin other than ethylene, and these may be used alone or in combination. The content of the ethylene is preferably 80% by weight or more in the copolymer of ethylene and an α-olefin other than ethylene, because the lower the content of ethylene, the lower the moldability of the obtained foam.

As the α-olefin, for example, 1
-Butene, 1-pentene, 1-hexene, 4-methyl-
1-pentene, 1-heptene, 1-octene and the like. As the content of the polyethylene resin decreases, the moldability of the obtained foam decreases, and as the content increases, the heat resistance of the obtained foam decreases.
It is limited to 0 to 60% by weight, preferably 15 to 55% by weight.

The crosslinking aid used in the present invention includes, for example, divinylbenzene, trimethylolpropane tri (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and 1,9-nonanediol di (meth) acrylate. ) Acrylate, 1,10-decanediol di (meth) acrylate, triallylic acid triallyl ester, triallyl isocyanurate, ethylvinylbenzene, etc., which may be used alone or in combination .

Regardless of whether the amount of the crosslinking aid is small or large, the moldability of the obtained foam is reduced.
The amount is limited to 0.5 to 10 parts by weight, preferably 0.8 to 6 parts by weight, based on 100 parts by weight of the resin matrix.

Examples of the pyrolytic foaming agent used in the present invention include azodicarbonamide, benzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, 4,4-oxybis (benzenesulfonylhydrazide) and the like. And
These may be used alone or in combination.

When the amount of the above-mentioned pyrolytic foaming agent is small, the foamability of the obtained foam is reduced, and when the amount is large, the strength of the obtained foam is reduced.
The amount is limited to 1 to 50 parts by weight, preferably 4 to 25 parts by weight based on 00 parts by weight.

The composition of the foamable polyolefin-based resin composition of the present invention is as described above. However, as long as the physical properties of the obtained foam are not impaired, oxidation of phenol-based, phosphorus-based, amine-based, sulfur-based, etc. Inhibitor, metal harm inhibitor, flame retardant,
Fillers, antistatic agents, stabilizers, pigments and the like may be added.

As a method for producing a foam using the foamable polyolefin resin composition of the present invention, for example, a predetermined amount of a resin matrix, a crosslinking assistant and a pyrolytic foaming agent are supplied to an extruder and melted. The foamed polyolefin-based resin sheet is kneaded and extruded to obtain a foamable polyolefin-based resin sheet, and the obtained foamable polyolefin-based resin sheet is irradiated with a predetermined amount of ionizing radiation and crosslinked to obtain a foamable polyolefin-based resin crosslinked sheet. A method in which a crosslinked polyolefin resin sheet is supplied to a foaming furnace and foamed by heating is used.

Examples of the ionizing radiation include α
Ray, β ray, γ ray and the like. The irradiation amount of the ionizing radiation is preferably 1 to 20 Mrad because the moldability of the obtained foam is reduced even if the irradiation amount is small or large.

The apparatus used for melt-kneading the resin matrix includes, for example, a single screw extruder,
Twin screw extruder, Banbury mixer, kneader mixer,
Rolls and the like.

[0021]

Next, embodiments of the present invention will be described. In addition,
“Parts” means “parts by weight”. Example 1 (1) Production of foamable polyolefin-based resin sheet As a polypropylene-based resin, 70 parts of an ethylene-propylene copolymer having an ethylene content of 4% by weight and a weight average molecular weight / number average molecular weight of 4.1. As a polyethylene resin, the melt index (MI) is 7 g / 1.
0 minutes, 30 parts of polyethylene having a density of 0.920 g / cm ³ , 3 parts of divinylbenzene as a crosslinking aid,
13 parts of azodicarbonamide as a thermal decomposition type blowing agent, 0.3 parts of 2,6-di-t-butyl-p-cresol and 0.3 part of dilaurylthiopropionate as antioxidants
Part, methylbenzotriazole 0.
5 parts were supplied to a single screw extruder [PCM-30, manufactured by Ikegai Iron Works Co., Ltd.], melted and kneaded at a temperature of 190 ° C. and extruded to a thickness of 1 m.
m of a foamable polyolefin resin sheet was obtained.

(2) Production of polyolefin-based resin foam The obtained foamable polyolefin-based resin sheet is irradiated with 3 Mrad of ionizing radiation at an accelerating voltage of 700 KV and crosslinked to obtain a foamed polyolefin-based resin crosslinked sheet. The foamed polyolefin-based resin crosslinked sheet is supplied to a vertical hot-air foaming furnace, the furnace temperature is 250 ° C., the approach speed is 1.7 m / sec,
The film was continuously stretched at a winding speed of 6.2 m / sec and heated and foamed to obtain a polyolefin resin foam.

(3) Production of Laminate The surface of the obtained polyolefin resin foam is subjected to corona discharge treatment, and a two-component curable polyester adhesive [polyester (manufactured by Hitachi Chemical Co., Ltd., trade name: Hybon), isocyanate] (Sumitomo Bayer Urethane Co., Ltd., product name: D
esmodur (R)] and bonded to a 0.65 mm-thick mixed resin sheet of a vinyl chloride resin and an acrylonitrile-butadiene-styrene copolymer resin to obtain a laminate.

Examples 2 to 5 and Comparative Examples 1 to 3 The same procedures as in Example 1 were carried out except that a predetermined amount (parts) of an ethylene-propylene copolymer, polyethylene and a crosslinking aid shown in Tables 1 and 2 were used. Thus, an expandable polyolefin-based resin sheet, a polyolefin-based resin foam, and a laminate were obtained.

[0025]

[Table 1]

[0026]

[Table 2]

Evaluation of Expandable Polyolefin Resin Sheet The ratio of the weight average molecular weight of the expandable polyolefin resin sheets obtained in Examples 1 to 5 and Comparative Examples 1 to 3 before and after irradiation with ionizing radiation was evaluated. Was measured and evaluated, and the obtained results are shown in Tables 3 and 4. The above measurement was performed for each of the irradiation doses of 2 and 4 Mrad.

[0028]

[Table 3]

[0029]

[Table 4]

Evaluation of Polyolefin Resin Foam The apparent density (g / g) of the polyolefin resin foams obtained in Examples 1 to 5 and Comparative Examples 1 to 3 was measured.
cm ³ ) and the residue of xylene extraction (% by weight) at 120 ° C. were measured and further evaluated by examining heat resistance. The obtained results are shown in Tables 5 and 6.

The value of the residue of xylene extraction at 120 ° C. was determined by extracting 0.1 g of a polyolefin resin foam, crushing the bubbles, and adding 2 g in 50 ml of xylene at 120 ° C.
After holding for 4 hours, the dry weight (g) of the residue that had passed through a 200-mesh wire net was weighed and calculated by the following equation (3). Residual value (% by weight) = (dry weight of residue / 0.1) × 100 (3)

The above heat resistance is determined by hot pressing a polyolefin resin foam at a temperature of 140 ° C. and a pressure of 100 kg / cm ² ,
The bubbles in the polyolefin-based resin foam were observed. When the bubbles did not break, the result was indicated by ○, and when the bubbles were broken, the result was indicated by ×.

[0033]

[Table 5]

[0034]

[Table 6]

Evaluation of Laminate The laminate obtained in each of Examples 1 to 5 and Comparative Examples 1 to 3 was observed and evaluated for appearance, and then measured for H / D value to evaluate strength and formability. Then, the peel strength was measured to evaluate the adhesiveness between the polyolefin resin foam and the skin material, and the obtained results are shown in Tables 7 and 8. The above appearance is
When no swelling, dent, surface roughness, or the like was observed, the result was indicated by ○, and when even one portion was observed, the result was indicated by ×.

The H / D value was determined by heating the obtained laminate with a far-infrared heater to raise the temperature of the surface layer of the polyolefin resin foam to 150 to 160 ° C.
The molded product was vacuum-formed using a cylindrical female mold having a diameter of mm, the depth H (cm) and the diameter D (cm) of the obtained molded product were measured, and the ratio H / D was calculated.

The peel strength was measured using an autograph [DCS-500, manufactured by Shimadzu Corporation] using a test piece having a width of 25 mm and a length of 100 mm produced by cutting the obtained laminate.
0] at 20 ° C. or 120 ° C. for 5 minutes,
The strength (kg / 25 mm) at the time of peeling was measured.

[0038]

[Table 7]

[0039]

[Table 8]

[0040]

The composition of the foamable polyolefin resin composition of the present invention is as described above, so that it is hardly deteriorated even when irradiated with ionizing radiation, is excellent in heat resistance and moldability, and is excellent in skin material. A polyolefin-based resin foam having excellent adhesiveness can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-248847 (JP, A) JP-A-5-1170 (JP, A) JP-A-56-34732 (JP, A) JP-A 64-64 87641 (JP, A) JP-A-2-102234 (JP, A) JP-A-2-175227 (JP, A) JP-A-60-36535 (JP, A) JP-A-62-256842 (JP, A) JP-A-3-152136 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08J 9/00-9/42 C08L 23/04-23/16

Claims (1)

(57) [Claims] 1. A polypropylene resin comprising propylene and an α-olefin other than propylene as constituent units, wherein the α-olefin content is 2 to 10% by weight and the weight average molecular weight / number average molecular weight is 3 to 7 40-90% by weight
And 100 to 100 parts by weight of a resin matrix composed of 10 to 60% by weight of a polyethylene resin having a melt index of 2 to 50 g / 10 minutes, 0.5 to 10 parts by weight of a crosslinking aid, and 1 to 50 parts by weight of a pyrolytic foaming agent A foamable polyolefin-based resin composition comprising: