JP2851509B2 - 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
Since the molecular chains are easily broken due to ionizing radiation, peroxides, and the like used during crosslinking and foaming, a foam obtained by foaming a polyolefin resin containing a polyethylene resin in addition to a polypropylene resin is used. It has become.

As a method for producing the above-mentioned polyolefin resin foam, for example, Japanese Patent Publication No. 46-38716, Japanese Patent Publication No. 58-57452, and Japanese Patent Application Laid-Open No.
935, JP-B-63-1977, JP-A-6
In JP-A-4-87641 and the like, a method in which a polyolefin-based resin sheet is cross-linked by ionizing radiation and then foamed using a specific foaming agent has been proposed, but the cross-linking in the polyolefin-based resin is not uniform. In addition, there is a disadvantage that the foam of the obtained foam is also non-uniform and the moldability is low.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks, the present invention provides a foamable polyolefin-based resin composition capable of obtaining a foam having excellent heat resistance and moldability and excellent adhesion to a skin material. The purpose is to provide things.

[0006]

The resin matrix used in the present invention comprises a polyethylene resin and a polypropylene resin. The elution amount of o-dichlorobenzene by the cross fractionation method of the polyethylene resin is
At 40 ° C., the heat resistance of the obtained foam decreases as the content increases, so the content is limited to 20% by weight or less, preferably 17% by weight or less, more preferably 14% by weight or less.

The amount of the polyethylene resin eluted with o-dichlorobenzene by the cross fractionation method is 60 to 80 ° C.
, The moldability of the obtained foam is reduced when the amount is reduced, and the heat resistance of the obtained foam is reduced when the amount is increased, so the content is limited to 30 to 85% by weight, preferably 35 to 7% by weight.
It is 5% by weight, more preferably 40 to 70% by weight.

The amount of the polyethylene resin eluted with o-dichlorobenzene by the cross fractionation method is 85 to 100.
At 0 ° C, the heat resistance of the obtained foam decreases when the temperature decreases, and the flexibility of the obtained foam decreases when the temperature increases, so the content is limited to 7 to 35% by weight, preferably 10 to 30% by weight.
%, More preferably 13 to 28% by weight.

The weight-average molecular weight of the portion eluted with o-dichlorobenzene at 40 ° C. decreases as the heat resistance of the obtained foam decreases, and as it increases, the moldability of the obtained foam decreases. 1 × 10 ⁴ -8 × 10
⁴ and preferably 0.2 × 10 ^{4 to} 7.5 × 1
0 is ^4, and more preferably 0.3 × 10 ⁴ ~7 × 10
⁴

The weight-average molecular weight of the above-mentioned o-dichlorobenzene-eluted portion at 60 to 80 ° C. decreases as the heat resistance of the obtained foam decreases, and as it increases, the moldability of the obtained foam decreases. 2 × 10 ^{4 to} 25 ×
10 ⁴ , preferably 2.5 × 10 ⁴ -24 ×
10 ⁴ , more preferably 3 × 10 ^{4 to} 22 × 10 ^4
4

[0011] The weight-average molecular weight of the portion eluted with o-dichlorobenzene at 85 to 100 ° C decreases as the heat resistance of the obtained foam decreases, and as it increases, the moldability of the obtained foam decreases. 4 × 10 ⁴ -25
× 10 ⁴ , preferably 4.5 × 10 ⁴ to 23
× 10 ⁴ , more preferably 5 × 10 ^{4 to} 21 × 1
0 of ^4.

The measurement of the resin elution amount by the above-mentioned cross fractionation method is performed by the following operation. That is, the resin
Dissolve in o-dichlorobenzene at 140 ° C or at a temperature at which the resin completely dissolves to obtain a solution, cool the resulting solution at a constant rate, and apply a thin polymer to the surface of an inert carrier prepared in advance. Form a layer. At this time, the resin component is
It is produced in the order of high crystallinity and high molecular weight. Thereafter, the temperature is raised continuously or stepwise, the concentration of the resin component eluted sequentially is detected, and the composition distribution (crystallinity distribution) is measured (temperature-increased elution fractionation). At the same time, high-temperature GP
Molecular weight and molecular weight distribution of components eluted by C (Gas Phase Chromatograph) (weight average molecular weight / number average molecular weight)
Is measured.

The melt index (MI) of the above polyethylene resin is limited to 2 to 50 g / 10 minutes because the lower the melt index (MI), the lower the moldability of the obtained foam and the higher the melt index, the lower the heat resistance of the obtained foam. And preferably 3 to 30 g / 10 min, more preferably 4 to 25 g.
/ 10 minutes.

Examples of the polyethylene resin include ethylene homopolymer, ethylene and α other than ethylene.
-Olefin copolymers, etc., and these may be used alone or in combination. Examples of the α-olefin include propylene, 1-butene, 1
-Pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like.

The content of the above ethylene is preferably 80% by weight or more in a copolymer of ethylene and an α-olefin other than ethylene, since the lower the content of ethylene, the lower the moldability of the obtained foam. The content of the polyethylene-based resin is limited to 10 to 60% by weight in the resin matrix because the moldability of the obtained foam decreases when the content decreases, and the heat resistance of the obtained foam decreases when the content increases.
Preferably it is 15 to 55% by weight.

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,
Examples include 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like.

The content of the above-mentioned α-olefin is limited to 1 to 15% by weight in the polypropylene resin, and is preferably 1.5 -12% by weight, more preferably 2-10% by weight.

The molecular weight distribution (weight-average molecular weight / number-average molecular weight) of the above-mentioned polypropylene-based resin is from 2 to 5, since the moldability of the obtained foam decreases as the size decreases, and the heat resistance of the obtained foam decreases as the size increases. 8, preferably 2.2 to 7, more preferably 2.5 to 6
It is.

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

Examples of the crosslinking aid used in the present invention include 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 pyrolytic foaming agent is smaller, the foamability of the obtained foam is reduced, and when the amount is larger, 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 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 phenolic, phosphorus, amine, sulfur, etc. Inhibitor, metal harm inhibitor, flame retardant,
Fillers, antistatic agents, stabilizers, pigments and the like may be added.

The foamable polyolefin resin composition of the present invention is obtained by, for example, melt-kneading a predetermined amount of a resin matrix, a crosslinking aid and a pyrolytic foaming agent. Examples of the melt kneader used for the melt kneading include a single screw extruder, a twin screw extruder, a Banbury mixer, a kneader mixer, and a roll.

As a method for producing a foam using the foamable polyolefin resin composition, for example, a foamable polyolefin resin composition is formed into a sheet, and a foamable polyolefin resin sheet is obtained. A method of irradiating a predetermined amount of ionizing radiation to the foamable polyolefin-based resin sheet and crosslinking the foamed polyolefin-based resin sheet to obtain a foamed polyolefin-based resin cross-linked sheet, supplying the obtained foamable polyolefin-based resin cross-linked sheet to a foaming furnace, and heating and foaming the sheet. Is mentioned. As the ionizing radiation, for example, α-ray, β-ray, γ-ray,
Electron beam and the like. The dose of the ionizing radiation is
Since the moldability of the obtained foam is reduced regardless of the decrease or increase, 1 to 20 Mrad is preferable.

[0027]

Next, embodiments of the present invention will be described. Less than,
“Parts” means “parts by weight”. The measurement of the weight-average molecular weight of the portion eluted with o-dichlorobenzene by the cross fractionation method was carried out using a cross fractionation chromatograph (“CFC-T150A” manufactured by Mitsubishi Yuka Co., Ltd.), and the temperature was raised by 2 ° C. And the range from the lower limit to the upper limit of the obtained value was shown. Example 1 (1) Production of Polyolefin Resin Foam As a polyethylene resin, the elution amount of o-dichlorobenzene and the weight average molecular weight thereof by a cross fractionation method at a predetermined temperature are values shown in Table 1, and the melt index is shown. (MI) is 8 g / 10 min and density is 0.918
g / cm ³ of 30 parts of polyethylene, as a polypropylene resin, the ethylene content is 2.4% by weight,
Molecular weight distribution (weight average molecular weight / number average molecular weight) of 3.8
And a melt index (MI) of 0.5 g / 10
70 parts of ethylene-propylene copolymer, 2 parts of divinylbenzene as a crosslinking aid, 14 parts of azodicarbonamide as a pyrolytic foaming agent, and 2,6 as an antioxidant.
0.3 parts of di-t-butyl-p-cresol and 0.3 parts of dilaurylthiopropionate, and 0.5 parts of methylbenzotriazole as a metal harm inhibitor were fed to a twin-screw extruder at a temperature of 190 ° C. Extruded by melting and kneading with a thickness of 1mm
Was obtained. An accelerating voltage of 700 was applied to the obtained foamable polyolefin resin sheet.
Irradiating with 3 Mrad of ionizing radiation at kV and cross-linking to obtain a cross-linked foamable polyolefin-based resin sheet, the obtained cross-linked foamable polyolefin-based resin sheet is supplied to a vertical hot-air foaming furnace and continuously heated at a furnace temperature of 250 ° C. And heat-foamed to obtain a polyolefin-based resin foam.

(2) 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 (Hybon, manufactured by Hitachi Chemical Co., Ltd.), isocyanate (Sumitomo) "Desmodur" manufactured by Bayer Urethane
R ")], and bonded to a skin material composed of a mixed resin of a vinyl chloride resin and an acrylonitrile-butadiene-styrene copolymer resin having a thickness of 0.65 mm to obtain a laminate.

Examples 2 to 5 and Comparative Examples 1 to 5 Predetermined amounts of polyethylene and ethylene shown in Tables 1 and 2
A polyolefin resin foam and a laminate were obtained in the same manner as in Example 1 except that the propylene copolymer and the crosslinking aid were used.

[0030]

[Table 1]

[0031]

[Table 2]

Evaluation of Polyolefin Resin Foams The polyolefin resin foams obtained in the above Examples 1 to 5 and Comparative Examples 1 to 5 were evaluated by observing the presence or absence of microscopic bubbles and then examining the heat resistance. The evaluation was performed and the obtained results are shown in Table 3. The presence or absence of the extremely small bubbles was observed by observing the cross section of the polyolefin resin foam using a scanning electron microscope, and the presence of bubbles having a diameter of 20 μm or less was confirmed.
The above heat resistance is obtained by heating the polyolefin resin foam at a temperature of 14 ° C.
It was hot-pressed at 0 ° C. and a pressure of 100 kg / cm ² , and the bubbles in the polyolefin resin foam were observed. The case where no bubbles were broken was indicated by “○”, and the case where bubbles were broken was indicated by “×”.

[0033]

[Table 3]

Evaluation of laminate The laminates obtained in Examples 1 to 5 and Comparative Examples 1 to 5 were evaluated by observing the appearance, and then measuring the H / D value to evaluate the strength and moldability. 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 4 and 5. The above appearance is
When no swelling, dent, surface roughness, etc. were observed, the result was indicated by ○, and when even one portion was observed, the result was indicated by ×.

The H / D value is 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 determined by cutting a test piece having a width of 25 mm and a length of 100 mm produced by cutting the obtained laminate, using an autograph (“DCS-500” manufactured by Shimadzu Corporation).
0 "), the temperature (150 ° C) was maintained for 5 minutes, and then the strength (gf) when the skin material was peeled off was measured.

[0037]

[Table 4]

[0038]

[Table 5]

[0039]

Since the composition of the foamable polyolefin resin composition of the present invention is as described above, a polyolefin resin foam excellent in heat resistance and moldability and excellent in adhesion to a skin material is obtained. can get.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C08J 9/00-9/42 C08L 23/04-23/16

Claims (1)

(57) [Claims] 1. An o-dichlorobenzene by a cross fractionation method
Elution amount at 40 ° C. is 20% by weight or less,
30 to 85% by weight at ℃, 7 to 35% at 85 to 100 ° C
%, And the weight-average molecular weight of the elution portion at 40 ° C.
0.1 × 10 ^Four~ 8 × 10^FourElution part at 60-80 ° C
Weight average molecular weight of 2 × 10^Four~ 25 × 10^Four, 85
The weight average molecular weight of the eluted part at ~ 100 ° C is 4 × 10^Four
~ 25 × 10^FourAnd the melt index (MI) is
Polyethylene resin 10 to 6 which is 2 to 50 g / 10 minutes
0% by weight, propylene and α-olefin other than propylene
And the α-olefin content is 1
-15% by weight, and the molecular weight distribution (weight average molecular weight / number)
Average molecular weight) of 2 to 8, and a melt index (M
I) is 0.2 to 20 g / 10 min.
Resin matrix 10 comprising 40 to 90% by weight of resin
0 parts by weight, 0.5 to 10 parts by weight of a crosslinking aid and pyrolysis type
A foaming agent comprising 1 to 50 parts by weight of a foaming agent.
Liolefin resin composition.