JPH06287341A - Polyolefin resin foam - Google Patents

Abstract

PURPOSE:To provide a polyolefin resin foam which is excellent in moldability. CONSTITUTION:A polyolefin resin foam comprises 40-95wt.% polypropylene resin having an ethylene content of 2-15wt.% and a wt.-average mol.wt. of 2.5X10<5>6.0X10<5> and 5-60wt.% polyethylene resin, has an apparent density of 0.02-0.2g/cm<2> and a swelling ratio expressed by the formula of 30-80, and gives 20-60wt.% extraction residue when extracted with xylene at 120 deg.C for 24hr followed by drying at 80 deg.C under 10mmHg for 5hr.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyolefin resin foam.

[0002]

2. Description of the Related Art Polyolefin resin foams are excellent in flexibility and heat insulation and have been conventionally 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 made of a polyolefin resin containing a polypropylene resin having excellent heat resistance is mainly used. Has been.

However, polypropylene resins are
Since the molecular chain is easily broken by ionizing radiation, peroxide, etc. used at the time of cross-linking and foaming, a foamed body obtained by foaming a polyolefin resin containing a polyethylene resin in addition to the polypropylene resin is used. It's starting to happen.

In order to improve the moldability of the above-mentioned polyolefin resin foam, for example, in JP-A-63-1977, a polyolefin resin foam having a higher degree of internal cross-linking compared to the surface layer is proposed. However, the moldability was still insufficient.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above drawbacks, and an object thereof is to provide a polyolefin resin foam having excellent moldability.

[0006]

The polyolefin resin foam of the present invention comprises a polypropylene resin and a polyethylene resin. The polypropylene-based resin contains ethylene, the content of which decreases the moldability of the polyolefin-based resin foam when the content decreases, and decreases the heat resistance of the polyolefin-based resin foam when the content increases.
It is limited to 2 to 15% by weight in the polypropylene resin, preferably 2 to 10% by weight.

When the weight average molecular weight of the polypropylene resin is small, the foamability of the polyolefin resin foam is lowered, and when it is large, the flexibility of the polyolefin resin foam is lowered, and therefore 2.5 × 10 ^{5 to} 6 0.0 x 1
0 is limited to ^5, preferably 3.0 × 10 ⁵ to 5.0 ×
It is 10 ⁵ .

When the melt index (MI) of the polypropylene resin is small, the moldability of the polyolefin resin foam is lowered, and when it is large, the heat resistance of the polyolefin resin foam is lowered.
/ 10 minutes is preferable, and more preferably 0.3 to 5 g / 1.
0 minutes.

When the content of the polypropylene-based resin is low, the heat resistance of the polyolefin-based resin foam is reduced, and when it is high, the moldability of the polyolefin-based resin foam is reduced. The amount is limited to 40 to 95% by weight, preferably 45 to 85% by weight.

Examples of the polyethylene resin include ethylene homopolymer, ethylene and α other than ethylene.
-Copolymers with olefins and the like are mentioned, and these may be used alone or in combination. Examples of the α-olefin other than ethylene include 1-butene,
1-pentene, 1-hexene, 4-methyl-1 pentene, 1-heptene, 1-octene and the like can be mentioned.

Since the moldability of the polyolefin resin foam decreases when the content of ethylene decreases, it is preferably 80% by weight or more in the copolymer of ethylene and an α-olefin other than ethylene. When the melt index (MI) of the polyethylene resin is small, the moldability of the polyolefin resin foam is low, and when it is large, the heat resistance of the polyolefin resin foam is low. , Preferably 3
~ 30 g / 10 minutes.

When the content of the polyethylene resin is small, the moldability of the polyolefin resin foam decreases, and when it is large, the heat resistance of the polyolefin resin foam decreases, so that the total content of the polypropylene resin and the polyethylene resin is low. The amount is limited to 5 to 60% by weight, preferably 15 to 55% by weight.

The apparent density of the polyolefin-based resin foam of the present invention is 0.02 to 0.02 because the moldability of the polyolefin-based resin foam deteriorates even if the apparent density is decreased or increased.
Limited to 0.2 g / cm ³ .

120 of the above polyolefin resin foam
Immediately after xylene extraction at 80 ° C for 24 hours,
The residual amount after drying at mmHg for 5 hours is limited to 20 to 60% by weight because the moldability of the polyolefin-based resin foam deteriorates regardless of whether it is small or large. The above residual amount was obtained by collecting a predetermined amount (g) of a polyolefin resin foam, crushing the bubbles, and holding the mixture in 50 ml of xylene at a temperature of 120 ° C. for 24 hours, and immediately after passing through a 200-mesh wire net, a residual substance of 5 at ℃, 10mmHg
It is the amount when dried for an hour.

The swelling ratio of the polyolefin-based resin foam is limited to 30 to 80 because the moldability of the polyolefin-based resin foam deteriorates as the swelling ratio decreases or increases.

The swelling ratio was measured by measuring the residual amount immediately after the xylene extraction at 120 ° C. for 24 hours and the residual amount immediately after the xylene extraction at 120 ° C. for 24 hours and after drying at 80 ° C. and 10 mmHg for 5 hours. , Is calculated by the following equation (1).

[0017]

[Equation 2]

The polyolefin resin foam of the present invention comprises
It is obtained by foaming a polyolefin resin composition comprising a polypropylene resin, a polyethylene resin, a crosslinking aid, and a thermal decomposition type foaming agent. Examples of the crosslinking aid include divinylbenzene, trimethylolpropane tri (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decane. Examples thereof include diol di (meth) acrylate, trimellitic acid triallyl ester, triallyl isocyanurate, and ethyl vinyl benzene, and these may be used alone or in combination.

If the amount of the above-mentioned crosslinking aid added is small or large, the moldability of the resulting foam will be deteriorated.
0.5 to 10 parts by weight is preferable per 100 parts by weight of the total amount of polypropylene resin and polyethylene resin,
It is more preferably 0.8 to 6 parts by weight.

Examples of the thermal decomposition type foaming agent include azodicarbonamide, benzenesulfonyl hydrazide,
Examples thereof include dinitrosopentamethylenetetramine, toluenesulfonyl hydrazide, and 4,4-oxybis (benzenesulfonyl hydrazide). These may be used alone or in combination.

When the amount of the thermal decomposition type foaming agent added is small, the foamability of the resulting foam is low, and when the amount is high, the strength of the resulting foam is low. Therefore, the total amount of polypropylene resin and polyethylene resin is 1 to 50 parts by weight is preferable with respect to 100 parts by weight, and more preferably 4 to 25 parts by weight.
Parts by weight.

The composition of the polyolefin-based resin foam of the present invention is as described above, but within the range that does not impair the physical properties of the polyolefin-based resin foam, phenol-based, phosphorus-based,
Amine-based and sulfur-based antioxidants, metal damage inhibitors, flame retardants, fillers, antistatic agents, stabilizers, pigments and the like may be added.

The polyolefin resin composition used for producing the polyolefin resin foam of the present invention is
For example, it can be obtained by melt-kneading a predetermined amount of polypropylene-based resin, polyethylene-based resin, crosslinking aid and thermal decomposition type foaming agent. For the melt-kneading, for example, a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader mixer, a roll or the like is used.

As the method for producing the above-mentioned polyolefin resin foam, for example, the above-mentioned polyolefin resin composition is molded into a sheet to obtain a foamable polyolefin resin sheet, and the obtained foamable polyolefin resin sheet is subjected to electronic A method may be mentioned in which a predetermined amount of a wire is irradiated and crosslinked to obtain a foamable polyolefin-based resin crosslinked sheet, and the obtained foamable polyolefin-based resin crosslinked sheet is supplied to a foaming furnace to heat and foam. Since the moldability of the polyolefin-based resin foam will be reduced if the irradiation amount of the electron beam is decreased or increased, it is preferably 1 to 8 Mrad, more preferably 1 to 3.5 Mrad.

[0025]

EXAMPLES Next, examples of the present invention will be described. In addition,
"Parts" means "parts by weight". Example 1 (1) Production of Polyolefin Resin Foam As a polypropylene resin, ethylene content is 3.5.
60% by weight of ethylene-propylene copolymer having a weight average molecular weight of 4.7 × 10 ⁵ and a melt index (MI) of 0.5 g / 10 min. Polyethylene 4 having a 5.5 × 10 ⁴ , a melt index (MI) of 7 g / 10 minutes and a density of 0.920 g / cm ^3.
0 part, 3.5 parts of divinylbenzene as a crosslinking aid, 13 parts of azodicarbonamide as a thermal decomposition type foaming agent, 0.3 part of 2,6-di-t-butyl-p-cresol as an antioxidant and dilauryl. 0.3 parts of thiopropionate,
0.5 parts of methylbenzotriazole as a metal damage inhibitor was supplied to a twin-screw extruder (“PCM-30” manufactured by Ikegai Tekko KK), melt-kneaded at a temperature of 190 ° C. and extruded to a thickness of 1 mm.
To obtain a foamable polyolefin resin sheet.

The resulting expandable polyolefin resin sheet was exposed to an ionizing radiation of 2.5 Mra at an acceleration voltage of 700 kV.
d) Irradiated and crosslinked to obtain a foamable polyolefin-based resin crosslinked sheet, and the obtained foamable polyolefin-based resin crosslinked sheet was placed in an oven and freely foamed at a temperature of 250 ° C. for 5 minutes to obtain a polyolefin-based resin foam. .

(2) Manufacture of Laminated Body 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 Polymer Co., Ltd.), isocyanate (Sumitomo "Desmodur" manufactured by Bayer Urethane Co., Ltd.
R ″)] was used to adhere to a skin material made of a mixed resin of vinyl chloride resin and acrylonitrile-butadiene-styrene copolymer resin having a thickness of 0.65 mm to obtain a laminate.

Examples 2-5 Predetermined amounts of ethylene-propylene copolymers shown in Table 1,
A polyolefin resin foam and a laminate were obtained in the same manner as in Example 1 except that polyethylene and a crosslinking aid were used and the predetermined amount of electron beam shown in Table 3 was irradiated.

Example 6 A predetermined amount of ethylene-propylene copolymer shown in Table 1,
An expandable polyolefin resin crosslinked sheet was obtained in the same manner as in Example 1 except that polyethylene and a crosslinking aid were used and the predetermined amount of electron beam shown in Table 3 was irradiated, and the obtained expandable polyolefin resin crosslinked sheet was obtained. Is fed to a vertical hot air foaming furnace and continuously stretched at a temperature of 230 ° C. to foam to obtain a polyolefin resin foam, and the obtained polyolefin resin foam is laminated in the same manner as in Example 1. Got the body

Comparative Examples 1 to 4 A predetermined amount of ethylene-propylene copolymer shown in Table 2,
A polyolefin resin foam and a laminate were obtained in the same manner as in Example 1 except that polyethylene and divinylbenzene were used and the predetermined amount of electron beam shown in Table 3 was irradiated.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

Evaluation of Polyolefin Resin Foams The apparent density of the polyolefin resin foams obtained in Examples 1 to 6 and Comparative Examples 1 to 4 was 12
Immediately after xylene extraction at 0 ° C. for 24 hours, 80 ° C., 1
The residual amount and the swelling ratio after drying at 0 mmHg for 5 hours were measured, and the obtained results are shown in Tables 4 and 5.

[0035]

[Table 4]

[0036]

[Table 5]

Evaluation of Laminates The laminates obtained in Examples 1 to 6 and Comparative Examples 1 to 4 above were observed and evaluated for appearance, and then H / D values were measured to evaluate strength and formability. Table 6 shows the obtained results.
And 7 are shown. The appearance is shown by ◯ when no swelling, dents, surface roughness, etc. were visually observed, and by × when one spot was observed.

The above H / D value was obtained by heating the obtained laminate with a far infrared heater to raise the temperature of the surface layer portion of the polyolefin resin foam to 150 to 160 ° C.
Vacuum molding was carried out using a cylindrical female mold of mm, and the depth H (cm) and diameter D (cm) of the obtained molded product were measured to calculate the ratio H / D.

[0039]

[Table 6]

[0040]

[Table 7]

[0041]

The composition of the polyolefin resin foam of the present invention is as described above, so that it has excellent moldability.

Claims (1)

[Claims] 1. The ethylene content is 2 to 15% by weight, and the weight average molecular weight is 2.5 × 10 ^{5 to} 6.0 × 10 ^5.
The polypropylene-based resin is 40 to 95% by weight and the polyethylene-based resin is 5 to 60% by weight, and the apparent density is 0.02 to 0.2 g / cm ³ , 120 ° C, immediately after xylene extraction for 24 hours, 80 ° C, The residual amount after drying at 10 mmHg for 5 hours is 20 to 60% by weight and the formula (1)
A swelling ratio represented by is 30 to 80, and a polyolefin resin foam. [Equation 1]