JP3398451B2 - Crosslinked polyolefin resin foam - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crosslinked polyolefin resin foam, and more particularly to a crosslinked polyolefin resin foam having excellent heat resistance and flexibility and capable of being subjected to secondary processing in a complicated shape.

[0002]

2. Description of the Related Art Polyolefin resin foams are generally superior in flexibility and heat insulation,
It has been used as a vehicle interior material such as doors and instrument panels. These interior materials are usually molded into a predetermined shape by subjecting a sheet-shaped polyolefin resin foam to secondary processing such as vacuum molding and compression molding. The polyolefin resin foam is usually used and processed as a laminate in which a polyvinyl chloride resin sheet, a thermoplastic elastomer sheet, a natural or artificial cloth-like material, and a skin material such as leather are laminated.

By the way, in recent vacuum molding and compression molding of foams, rapid heating and an increase in processing temperature are required to improve productivity, and high temperature conditions of 120 to 200 ° C. are adopted. There is. Further, in the recent field of molding foams, it is required to be capable of molding into a complicated shape and deep drawing. Therefore, the polyolefin resin foam is required to have good moldability at high temperature. However, conventional polyethylene-based resin foams are not suitable for molding under such high temperature conditions because they have excellent flexibility but insufficient heat resistance. On the other hand, the crosslinked polypropylene-based resin foam has the highest melting point among the polyolefin-based resins and is excellent in heat resistance, but in the high temperature range of 140 to 160 ° C., the extensibility rapidly decreases and the moldability is high. Is reduced.

Therefore, conventionally, a resin composition comprising a polypropylene-based resin and a polyethylene-based resin is crosslinked and foamed to compensate for the defects of both. However, polypropylene-based resins are inferior in flexibility to polyethylene-based resins, so it is necessary to add a considerable amount of polyethylene-based resin in order to obtain a foam having sufficient flexibility. The heat resistance and moldability at high temperature are deteriorated, and when a heavy object is placed on the foam when used as an interior material, there arises a problem that the part under pressure is dented and the part is not recovered.

Conventionally, in order to improve the flexibility, heat resistance, secondary workability, etc. of polyolefin resin foams, for example,
A method for producing a crosslinked polyolefin foam in which a specific crosslinking aid such as a di- or triallyl ester of cyanuric acid or isocyanuric acid is blended with a polyolefin, particularly polypropylene, to crosslink and foam (JP-B-58-57452).
No.), a method of providing a difference in the degree of crosslinking between the surface layer and the inside of the crosslinked polypropylene foam (Japanese Patent Publication No. 63-1977). In these methods, although it is possible to achieve a certain degree of improvement in heat resistance by increasing the degree of crosslinking, the flexibility is impaired and the product becomes harder than necessary.

Further, by cross-linking and foaming a resin composition consisting of a propylene-ethylene random copolymer and a linear low density polyethylene obtained by copolymerizing octene-1, the mechanical properties and heat resistance peculiar to polypropylene can be obtained. A method for producing a crosslinked foam excellent in secondary processability without damage has been proposed (JP-A-4-80238). However, according to this method, although the strength of the resin matrix itself is excellent, it is difficult to obtain a foam having a uniform cell structure because the viscosity of the molten resin becomes uneven during foaming.

[0007] As described above, various proposals have been made to improve flexibility, heat resistance, secondary processability, etc. of polyolefin resin foams, but especially under conditions near and above the melting point. There may be problems in the strength and elongation of the foam, and as a result, it is difficult to carry out secondary processing of complicated and deep shapes, or even if molding processing is possible, heat resistance becomes insufficient. There was a problem that it would end up.

On the other hand, in recent years, by using a metallocene compound (metallocene catalyst) as an α-olefin polymerization catalyst, studies have been conducted to polymerize a polyolefin having a copolymer component uniformly present in the molecular chain and having a narrow molecular weight distribution. (Japanese Patent Application Laid-Open Nos. 3-188092 and 4-27959)
No. 2), and the possibility of new polyethylene resin is expected. However, no proposal has been made regarding foaming of a polyethylene resin obtained by using a metallocene compound as a polymerization catalyst.

[0009]

The object of the present invention is to provide a crosslink having high heat resistance and good flexibility, excellent secondary molding workability and compression strain recovery, and having a uniform cell shape and a beautiful appearance. It is to provide a polyolefin resin foam. As a result of intensive studies to overcome the above-mentioned problems of the prior art, the present inventors have made a polypropylene resin having a specific melt index as a resin component, and a metallocene compound containing a tetravalent transition metal as a polymerization catalyst. Using a specific polyethylene-based resin obtained by using in a specific ratio,
It has been found that the above object can be achieved by crosslinking and foaming this resin component using a polyfunctional monomer and an organic thermal decomposition type foaming agent.

The resin composition containing the resin component, the polyfunctional monomer, and the organic thermal decomposition type foaming agent can be uniformly crosslinked efficiently and continuously by irradiating with ionizing radiation. And when heat-foamed, heat resistance,
It is possible to obtain a crosslinked polyolefin resin foam which is excellent in flexibility, toughness, secondary molding workability without blistering and blurring, and compression strain recovery, and which is uniform in appearance. The present invention has been completed based on these findings.

[0011]

According to the present invention, (1)
(A) A polypropylene resin having a melt index within the range of 0.1 to 12 and more than 50% by weight and 90% by weight.
The following , and (b) a polyethylene resin 1 obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst
100 parts by weight of a resin component containing 0% by weight or more and less than 50% by weight, (2) 0.1 to 10 parts by weight of a polyfunctional monomer, and (3) 1 to 50 parts by weight of an organic thermal decomposition type foaming agent. After molding the polyolefin resin composition into a predetermined shape,
A crosslinked polyolefin resin foam characterized by being crosslinked and foamed, wherein the polyethylene resin has a density of 0.860 to 0.950 g / cm ³ and is eluted by 10% by weight by a cross fractionation method. The width of the temperature at the end of 100% by weight elution from the temperature of 30 is 30 ° C. or less, and the value of weight average molecular weight / number average molecular weight is 1.5 to 3.
There is provided a crosslinked polyolefin resin foam of No. 5. (Hereinafter, described as "the present invention 1") According to the present invention, (1) (a) the melt index is 0.1 to 1
More than 50% by weight of polypropylene resin within the range of 2
100 parts by weight of a resin component containing 90% by weight or less and (b) 10% by weight or more and less than 50% by weight of a polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, (2 ) Polyfunctional monomer 0.1-1
A crosslinked polyolefin resin foam obtained by molding a polyolefin resin composition containing 0 part by weight and (3) 1 to 50 parts by weight of an organic pyrolyzable foaming agent into a predetermined shape, and then crosslinking and foaming the resin composition. The polyethylene resin has one crystal melting peak measured using a differential scanning calorimeter (DSC), and the temperature range from the melting peak temperature to the end of melting of all crystals is within 20 ° C. A crosslinked polyolefin resin foam is provided. (Hereinafter, referred to as “present invention 2”.) Further, according to the present invention, (1)
(A) A polypropylene resin having a melt index within the range of 0.1 to 12 and more than 50% by weight and 90% by weight.
The following , and (b) a polyethylene resin 1 obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst
100 parts by weight of a resin component containing 0% by weight or more and less than 50% by weight, (2) 0.1 to 10 parts by weight of a polyfunctional monomer, and (3) 1 to 50 parts by weight of an organic thermal decomposition type foaming agent. After molding the polyolefin resin composition into a predetermined shape,
A cross-linked polyolefin resin foam formed by cross-linking and foaming, wherein the polyethylene resin is a differential scanning calorimeter (DS).
C), the number of crystal melting peaks is one, and the temperature range from the melting peak temperature to the end of melting of all the crystals is within 20 ° C., and the differential scanning calorimeter (DSC) is used. There is provided a crosslinked polyolefin resin foam having one crystal melting peak measured by using, and having a temperature range within 20 ° C. from the melting peak temperature until all the crystals are melted. (Hereinafter, referred to as "present invention 3")

The present invention will be described in detail below. (Polypropylene Resin) The polypropylene resin used in the present invention is a homopolymer of propylene or α other than propylene and propylene.
A copolymer with an olefin. Examples of the α-olefin as a copolymerization component include ethylene, 1-butene, 1
-Pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 3,3-dimethyl-
1-hexene and the like can be mentioned. The copolymer usually has a propylene component content of 85% by weight or more, preferably 90% by weight or more.
It is more than weight%.

The polypropylene resin used in the present invention has a melt index (hereinafter abbreviated as "MI":
0.1-12, measured according to ASTM D-1238)
It is necessary to be (g / 10 minutes). If the MI of the polypropylene resin used is too small, the moldability of the resulting foam will decrease, while if it is too large, the heat resistance of the resulting foam will decrease. MI is preferably 0.3 to
10 (g / 10 minutes), more preferably 0.5 to 8 (g /
10 minutes). The proportion of polypropylene resin in the resin component must be in the range of more than 50% by weight and 90% by weight or less , preferably more than 50% by weight.
It is 85% by weight or less . If the blending ratio of the polypropylene-based resin is too small, the heat resistance of the resulting foam will be lowered, and conversely, if it is too large, the foam will be harder than necessary and the moldability will be deteriorated.

(Polyethylene Resin) Examples of the polyethylene resin used in the present invention include ethylene homopolymers and ethylene / α-olefin copolymers. Examples of the α-olefin include propylene, 1-butene, 1-pentene,
1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like can be mentioned. The polyethylene resin used in the present invention 1 or 3 has a density of 0.860-0.
In the range of 950 g / cm ³ , from the temperature (T ₁ ) at the time of 10% by weight elution by the cross fractionation method described below to 100
Temperature (T ₂ ) width (T ₂ −T
₁ ) is 30 ° C. or less, and the weight average molecular weight / number average molecular weight (Mw / Mn) value is 1.5 to 3.5.

The polyethylene resin used in the present invention 2 or 3 has one crystal melting peak measured by using a differential scanning calorimeter (DSC), and the total melting point temperature (T ₃ ) The width (T ₄ -T ₃ ) of the temperature (T ₄ ) until the crystal is completely melted is within 20 ° C. By using a polyethylene-based resin having such characteristics, it is possible to obtain a flame-retardant foam having good foaming characteristics, a uniform cell shape, and a beautiful appearance when used in combination with a specific flame-retardant system. You can The polyethylene resin having these properties can be obtained by polymerizing ethylene or ethylene and an α-olefin using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst.

Metallocene Compound The metallocene compound generally means a compound having a structure in which a transition metal is sandwiched between π-electron unsaturated compounds, and a bis (cyclopentadienyl) metal complex is typical. More specifically, as the metallocene compound in the present invention, a tetravalent transition metal such as titanium, zirconium, nickel, palladium, hafnium, or platinum is provided with one or more cyclopentadienyl rings or an analogue thereof as a ligand ( The compound which exists as a ligand) is mentioned. The metallocene compound is also referred to as a metallocene catalyst because it is used as a polymerization catalyst.

Specific examples of the ligand include cyclopentadienyl ring; cyclopentadienyl ring substituted with a hydrocarbon group, a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group; cyclopentadienyl oligomer ring; indenyl ring And an indenyl ring substituted with a hydrocarbon group, a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group, and the like. In addition to these π-electron unsaturated compounds, as ligands, monovalent anion ligands such as chlorine and bromine, or divalent anion chelate ligands, hydrocarbons, alkoxides, arylamides, aryloxides, amides, arylamides , Phosphide, arylphosphide and the like may be coordinate-bonded to the transition metal atom.

Examples of the hydrocarbon group substituted on the cyclopentadienyl ring include methyl, ethyl, propyl, butyl, amyl, isoamyl, hexyl, isobutyl, heptyl, octyl, nonyl, decyl, cetyl, 2-ethylhexyl and phenyl. Etc.

Examples of such metallocene compounds include cyclopentadienyl titanium tris (dimethylamide), methylcyclopentadienyl titanium tris (dimethylamide), bis (cyclopentadienyl) titanium dichloride, and dimethylsilyltetramethyl. Cyclopentadienyl-tert-butylamide zirconium dichloride, dimethylsilyltetramethylcyclopentadienyl-tert-butylamide hafnium dichloride, dimethylsilyltetramethylcyclopentadienyl-pn-butylphenylamide zirconium chloride, methylphenylsilyl Tetramethylcyclopentadienyl-tert-butylamide hafnium dichloride, indenyl titanium tris (dimethylamide), indenyl tita Umutorisu (diethylamide), indenyl titanium tris (di -n- propyl amide), indenyl titanium bis (di -n- butylamide) (di -n- propyl amide) and the like.

The metallocene compound exhibits a function as a catalyst in the polymerization of various olefins by changing the kind of metal and the structure of the ligand and combining with a specific cocatalyst (cocatalyst). More specifically, the polymerization is usually carried out in a catalyst system in which methylaluminoxane (MAO) as a cocatalyst, a boron compound and the like are added to these metallocene compounds. The ratio of the cocatalyst used to the metallocene compound is 1
0 to 1,000,000 molar times, preferably 50 to 5,
It is 000 mole times. The polymerization conditions are not particularly limited, and for example, a solution polymerization method using an inert medium, a bulk polymerization method in which an inert medium does not substantially exist, a gas phase polymerization method and the like can be used. The polymerization temperature is usually -100 ° C to 300 ° C, and the polymerization pressure is usually atmospheric pressure to 100 kg / c.
Generally, m ² is used.

The metallocene catalyst is characterized in that the properties of active sites are uniform. Since the metallocene catalyst has the same activity at each active site, the homogeneity of the molecular weight, the molecular weight distribution, the composition, and the composition distribution of the polymer to be synthesized is improved. Therefore, the polyolefins polymerized with these metallocene catalysts have a narrow molecular weight distribution, and in the case of a copolymer, the copolymer components are introduced in almost equal proportions in every molecular weight component. Examples of the polyethylene resin obtained by using the metallocene compound as a polymerization catalyst include, for example,
Dow Chemical's CGCT and Exxon Chemical's EXACT are commercially available.

Cross fractionation method The cross fractionation method used in the present invention is as follows. First, the polyethylene resin is dissolved in o-dichlorobenzene at 140 ° C. or a temperature at which the polyethylene resin is completely dissolved, and then cooled at a constant rate,
On the surface of an inert carrier prepared in advance, thin polymer layers are formed in the order of high crystallinity and high molecular weight. Next, raise the temperature continuously or stepwise, and detect the concentration of the eluted components in order to obtain the composition distribution (crystallinity distribution).
To measure. The temperature rising elution fractionation (Tempera
true Rising Elution Fract
Ionation; TREF). At the same time, the components that were sequentially eluted were added to the high temperature GPC (Size Exclusi).
on Chromatograph; SEC) to determine the molecular weight and molecular weight distribution. In the present invention,
The above-mentioned data was measured using a cross fractionation chromatograph device (Model CFC-T150A manufactured by Mitsubishi Petrochemical Co., Ltd.) equipped with both the temperature rising elution fractionation part and the high temperature GPC part described above as a system.

The polyethylene resin used in the present invention 1 or 3 has a temperature range from the temperature at the time of elution of 10% by weight to that at the end of 100% by weight elution by the cross fractionation method of 30.
C. or lower, preferably 28.degree. C. or lower. This temperature range is 3
When the temperature is higher than 0 ° C, a component having high crystallinity and a component having low crystallinity are present in the polyethylene resin at the same time, and the viscosity of the molten resin is uneven during foaming, and a uniform foam can be obtained. Have difficulty.

The polyethylene-based resin used in the present invention 1 or 3 has a weight average molecular weight measured by a cross fractionation method /
The value of the number average molecular weight is 1.5 to 3.5, preferably 1.7.
Within the range of 3.0. If this value is less than 1.5, the strength of the foam will be improved, but the resin will not flow easily during melting, and molding will be difficult. On the other hand, when this value exceeds 3.5, the variation in the molecular weight distribution becomes large, the abundance ratio of low molecular weight molecules and high molecular weight molecules increases, and uneven viscosity occurs in the molten resin during foaming, resulting in uniform foaming. It is difficult to get a body.

Differential Scanning Calorimetric Analysis Differential scanning calorimetric analysis in the present invention was carried out by the following method. About 10 mg of polyethylene resin sample was put in a platinum pan and measured with a differential scanning calorimeter (DSC: SSC5200 manufactured by Seiko Instruments Inc.). The measurement conditions were such that the sample was melted once, cooled to −50 ° C. at a rate of 5 ° C./minute, and then heated at a rate of 5 ° C./minute for measurement. The polyethylene resin used in the present invention 2 or 3 has one crystal melting peak in differential scanning calorimetry,
The temperature range from the melting peak temperature to the end of melting of all crystals is within 20 ° C. The single crystal melting peak includes the case where the peak is not clearly divided into two or more peaks.

The presence of a plurality of crystal melting peaks means that a plurality of components having different crystallinity are present. In that case, the viscosity of the molten resin becomes uneven at the time of foaming, and a uniform foamed product is obtained. Hard to get. Even if there is only one melting peak, if the temperature range from the melting peak temperature to the end of melting of all the crystals exceeds 20 ° C, the crystallinity between the molecules in the polyethylene resin will be high and the crystallinity will be low. The difference in crystallinity becomes large, and the viscosity of the molten resin becomes uneven at the time of foaming, which makes it difficult to obtain a uniform foam.

The polyethylene resin used in density present invention 1 or 3, density 0.860~0.950g / cm ^3, preferably 0.8
It is in the range of 70 to 0.945 g / cm ³ . When the density is less than 0.860 g / cm ³ , the crystallinity of the polyethylene-based resin is low, and the heat resistance of the foam is lowered. On the contrary, when the density exceeds 0.950 g / cm ³ , the flexibility and the flexibility of the obtained foam are reduced. It causes problems in elongation.

(Polyfunctional Monomer) In the present invention, a polyfunctional monomer is used as a crosslinking aid.
Examples of the polyfunctional monomer include 1,2-benzenedicarboxylic acid diallyl ester, 1,3-benzenedicarboxylic acid diallyl ester, 1,4-benzenedicarboxylic acid diallyl ester, and 1,2,4-benzenetricarboxylic acid triallyl ester. , And aromatic polyvalent carboxylic acid polyvalent allyl esters such as these nuclear substitution compounds and related homologues. Examples of polyfunctional monomers include divinylbenzene, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, 1,9-nonanediol dimethacrylate, and 1,1.
0-decanediol dimethacrylate, triallyl isocyanurate, ethyl vinylbenzene, ethylene glycol dimethacrylate and the like can be used.

These polyfunctional monomers may be used alone or in combination of two or more. The polyfunctional monomer is used in a proportion of 0.1 to 10 parts by weight with respect to 100 parts by weight of the resin component. If the amount of the polyfunctional monomer added is too small or too large, the moldability of the resulting foam will be reduced. A preferred usage ratio of the polyfunctional monomer is 0.5 to 8 parts by weight.

(Organic Pyrolysis Foaming Agent) The organic pyrolysis foaming agent used in the present invention is a compound that decomposes to generate gas when heated, and specifically,
Examples include azodicarbonamide, oxybenzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, 4,4-oxybis (benzenesulfonylhydrazide), azobisisobutyronitrile, barium azodicarboxylic acid, and hydrazodicarbonamide. It These may be used alone,
You may use together. The organic thermal decomposition type foaming agent is a resin component 1
It is used in a proportion of 1 to 50 parts by weight with respect to 00 parts by weight. If the amount of the organic pyrolyzable foaming agent added is too small, the foamability of the resin composition will decrease, and if it is too large, the strength of the resulting foam will decrease. A preferred use ratio of the organic thermal decomposition type foaming agent is 4 to 25 parts by weight.

(Optional Components) In the present invention, other thermoplastic resins such as low-density polyethylene, within the range that does not impair the object of the present invention,
Linear low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene, ethylene-propylene rubber, polyvinyl acetate, polybutene and the like can be added as a minor component. Further, a phenol-based, phosphorus-based, amine-based or sulfur-based antioxidant, a metal damage inhibitor, a flame retardant, a filler, an antistatic agent, a stabilizer, a pigment or the like may be added.

(Method for Producing Foam) In the present invention, a polyolefin resin composition obtained by blending the above-mentioned components is molded into a predetermined shape and then crosslinked / foamed to produce a crosslinked polyolefin resin foam. To do. Specifically, for example, the following manufacturing method may be mentioned. A predetermined amount of the polyolefin resin composition is melt-kneaded at a temperature lower than the decomposition temperature of the thermal decomposition type foaming agent using a kneading device such as a single screw extruder, a twin screw extruder, a Banbury mixer, a kneader mixer, and a roll. Then, a foamable resin composition is prepared, and this is generally formed into a sheet. Next, the obtained expandable resin composition sheet is irradiated with a predetermined amount of ionizing radiation to crosslink the polyolefin resin, and then the crosslinked sheet is heated to a temperature equal to or higher than the decomposition temperature of the foaming agent to foam. Examples of the ionizing radiation include α rays, β rays, γ rays, electron beams and the like. Further, peroxide crosslinking or silane crosslinking can be performed instead of irradiation crosslinking with ionizing radiation.

The irradiation dose of the ionizing radiation varies depending on the kind of the polyfunctional monomer and the desired degree of crosslinking, but is usually 0.1 to 50 Mrad, preferably 0.5 to 20 M.
It is rad. If the irradiation dose is too low, the heat resistance of the foam obtained will be insufficient, and if it is too high, the foam will be too hard.

(Crosslinked Polyolefin Resin Foam) The crosslinked polyolefin resin foam of the present invention has a good appearance and has a uniform cell structure in which there are no maximum or minimum cell sizes. . Further, the crosslinked polyolefin resin foam of the present invention is excellent in heat resistance, flexibility, toughness, moldability, compressive strain recovery, and the like. The crosslinked polyolefin-based resin foam of the present invention has good secondary workability, and can be molded into a complex shape or a deep shape without damage by vacuum molding or compression molding at a high temperature of 140 to 160 ° C. It can be processed.

The reason why the crosslinked polyolefin resin foam of the present invention has such excellent physical properties is not always clear at this stage, but it is presumed as follows. In general, polypropylene resin is a crystalline resin,
It is disintegrating when exposed to ionizing radiation. Accordingly, the molecular weight of the polypropylene resin is lowered by the irradiation of the ionizing radiation when the crosslinking aid is not added.
In order to achieve uniform crosslinking, a sufficient molecular weight and affinity with a crosslinking aid are required. The range of the molecular weight satisfying both of these properties is limited, and the range of M defined by the present invention is limited.
It is considered that this can be realized by the polypropylene resin having I.

On the other hand, the polyethylene resin used in the present invention is a resin obtained by polymerization using a metallocene catalyst, but the polymerization reaction using the metallocene catalyst is characterized by uniform reaction active points. In addition, a polymer having the same molecular weight and the same degree of branching is generated. This phenomenon is greatly different from the case of the polymerization using a conventional Ziegler-Natta catalyst, and the most remarkable difference is the copolymerization of ethylene and α-olefin. In the polymerization using an ordinary catalyst, a large amount of α-olefin, which is a copolymerization component, is introduced into a polymer component having a low molecular weight, and hardly introduced into a polymer component having a high molecular weight. As a result, a very hard and highly crystalline component and a soft and low crystalline component are mixed in the produced resin. In the process of foaming, the growth process of bubbles in the molten resin and the crystallization of the resin,
Since it can be divided into the process of fixing the bubble cell by solidification, if the melt viscosity of the resin varies, it affects the bubble growth process, and if there is a difference in the crystallization speed, it affects the process of fixing the bubble cell. As a result, foaming failure due to gas escape and appearance failure due to variation in bubble diameter will occur.

On the other hand, in the case of polymerization with a metallocene catalyst, a polyethylene resin having little variation in molecular weight and crystallinity can be obtained, so that the above problems occur when foaming a resin composition containing the resin. Not considered. Furthermore, since it is considered that the branches are uniformly introduced into the polyethylene resin obtained by using the metallocene catalyst, the polyethylene resin is rich in elasticity as compared with a normal polyethylene resin, and the compression strain recovery property is also excellent. Seem.

[0038]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. In addition,
"Parts" means "parts by weight". The physical properties of the foam were evaluated by the following methods. <Appearance> The foam was visually observed and evaluated according to the following criteria. ◯: No blur, blisters, dents, surface roughening, etc. ×: There is one or more blurs, blisters, dents, surface roughening, etc. <Cell Shape> A cross-section of the foamed body was photographed with a scanning electron microscope S-2300 manufactured by Hitachi, Ltd. at a magnification of 50 times to find microscopic cells having a diameter of 20 μm or less and a diameter of 3 mm or more. The presence or absence of maximum bubbles was confirmed. <Vacuum Formability> The surface temperature of the foam is 15 with a far infrared heater.
It is heated to 0 ° C. to 160 ° C., vacuum forming is performed using a cylindrical female die having a diameter of 100 mm, and the depth H (cm) and diameter D (cm) at the time of the forming are measured, Ratio H
/ D was calculated. The larger the H / D value, the better the moldability. <Compressive strain recovery property> A weight of 100 g is placed on the foam and placed in an oven at 100 ° C for 30 minutes to remove the weight, and then at 30 ° C at 30 ° C.
After leaving for a minute, the recovery rate (%) of the thickness was measured. The higher the compression strain recovery rate, the better the compression strain recovery property.

Example 1 An ethylene-propylene random copolymer as a polypropylene resin (ethylene content = 4.0% by weight, MI =)
0.5 g / 10 minutes) 60 parts, a polyethylene resin obtained by using a metallocene compound as a polymerization catalyst as a polyethylene resin (EXACT2 manufactured by Exxon Chemical Co.)
009: Density = 0.922 g / cm ³ , weight average molecular weight / number average molecular weight = 2.2, cross-fractionation method and DSC measurement results are shown in Table 1. 40 parts, 2 parts of 1,2,4-benzenetricarboxylic acid triallyl ester as a crosslinking aid, 13 parts of azodicarbonamide as an organic thermal decomposition type foaming agent, and 2,6-di-t-butyl as an antioxidant. -0.3 parts of p-cresol, 0.3 parts of dilauryl thiodipropionate, and 0.5 parts of methylbenzotriazole as a metal damage inhibitor were supplied to a twin-screw extruder (type PCM87 manufactured by Ikegai Tekko KK). Then, the mixture was melt-kneaded at 190 ° C. and extruded to form a sheet having a thickness of 1 mm. The obtained expandable resin composition sheet was irradiated with an electron beam of 6.0 Mrad at an accelerating voltage of 600 kV to be crosslinked, and then the obtained crosslinked sheet was put in an oven and allowed to freely foam at 250 ° C. for 5 minutes to crosslink. A polyolefin resin foam was prepared. The obtained foam has an expansion ratio of 25 times (cm ³ / g),
The appearance was uniform. After the surface of the obtained crosslinked polyolefin resin foam is subjected to corona discharge treatment, a mixed resin sheet of vinyl chloride resin and acrylonitrile-butadiene-styrene copolymer (thickness is used by using a two-component curing type polyester adhesive. 0.65 mm) to make a laminate. The evaluation results of the obtained foam are shown in Table 1.

Example 2 An ethylene-propylene random copolymer as a polypropylene resin (ethylene content = 4.0% by weight, MI =)
0.5 g / 10 minutes) 70 parts, a polyethylene resin obtained by using a metallocene compound as a polymerization catalyst as a polyethylene resin (EXACT3 manufactured by Exxon Chemical Co.)
027: Density = 0.900 g / cm ³ , weight average molecular weight / number average molecular weight = 2.0, and results of cross fractionation and DSC are shown in Table 1. ) 30 parts, and 3 parts of trimethylolpropane trimethacrylate as a cross-linking aid, and the electron beam irradiation amount was 4.5 Mrad in the same manner as in Example 1 except that the cross-linked polyolefin resin foam and the foam thereof were used. A laminated body was obtained. The evaluation results of the obtained foam are shown in Table 1.

Example 3 An ethylene-propylene random copolymer as a polypropylene resin (ethylene content = 3.6% by weight, MI =)
85 parts, polyethylene resin obtained by using a metallocene compound as a polymerization catalyst as a polyethylene resin (EXACT4 manufactured by Exxon Chemical Co.)
011: Density = 0.85 g / cm ³ , weight average molecular weight / number average molecular weight = 2.1, cross fractionation method and DSC measurement results are shown in Table 1. ) 15 parts, and 6 parts of divinylbenzene as a cross-linking aid were used, and a cross-linked polyolefin resin foam and its laminate were prepared in the same manner as in Example 1 except that the electron beam irradiation amount was 3.0 Mrad. Obtained. The evaluation results of the obtained foam are shown in Table 1.

[0042] [ratio Comparative Examples 1] polyethylene usual obtained using the titanium trichloride catalyst as a resin linear low-density polyethylene (Idemitsu Ishikasha manufactured 1044D: Density = 0.925g / cm ^3, a weight average Molecular weight / number average molecular weight = 4.0, cross fractionation method and DSC
The measurement results of are shown in Table 1. A crosslinked polyolefin resin foam and a laminate thereof were obtained in the same manner as in Example 1 except that (1) was used. The evaluation results of the obtained foam are shown in Table 1.

[Comparative Example 2] A normal linear low-density polyethylene obtained by using a titanium trichloride-based catalyst as a polyethylene-based resin (Tosoh 43-1: density = 0.905 g / cm ³ , weight average) (Molecular weight / number average molecular weight = 4.4, cross fractionation method and DSC measurement results are as shown in Table 1.), except that the crosslinked polyolefin resin foam and its laminate were used in the same manner as in Example 1. Got the body The evaluation results of the obtained foam are shown in Table 1.

Comparative Example 3 A normal high-density polyethylene obtained by using a magnesium chloride-supported catalyst as a polyethylene resin (HZ2100J manufactured by Mitsui Petrochemical Co., Ltd .: density = 0.957 g / cm ³ , weight average molecular weight / number average). A crosslinked polyolefin resin foam and a laminate thereof were obtained in the same manner as in Example 1 except that the molecular weight was 11.0 and the results of the cross fractionation method and the DSC measurement were as shown in Table 1.). . The evaluation results of the obtained foam are shown in Table 1.

[Comparative Example 4] 70 parts of polypropylene homopolymer (MI = 14.0 g / 10 minutes) as a polypropylene resin, a polyethylene resin obtained by using a metallocene compound as a polymerization catalyst as a polyethylene resin (Exxon Chemical EXACT2009: Density = 0.922 g / cm ³ , weight average molecular weight / number average molecular weight = 2.2, the results of cross fractionation and DSC are as shown in Table 1.) Other than using 30 parts In the same manner as in Example 1, a crosslinked polyolefin resin foam and a laminate thereof were obtained. The evaluation results of the obtained foam are shown in Table 1.

[0046]

[Table 1]

(Footnote) (* 1) Mw = weight average molecular weight, Mn = number average molecular weight (* 2) T ₁ = temperature at which 10% by weight of all resins by cross fractionation analysis elute T ₂ = total by cross fractionation analysis Temperature at which 100% by weight of the resin ends to elute T ₂ −T ₁ = width of temperature (* 3) T ₃ = melting peak temperature by DSC analysis T ₄ = melting end temperature by DSC analysis T ₄ −T ₃ = width of temperature

The larger the value of H / D is, the better the moldability is, and it is necessary to be 1.0 or more in the case of ordinary door removal. However, from the results of Table 1, Examples 1 to 1 of the present invention are shown. It can be seen that all of the crosslinked foams of 3 are 1.0 or more, which are satisfactory values.

[0049]

EFFECTS OF THE INVENTION According to the present invention, a crosslinked polyolefin resin which is excellent in heat resistance, flexibility and compression strain recovery, and has good secondary processability such as complicated shape and deep drawing, and is beautiful. A foam is provided.

Claims (3)

(57) [Claims] (1) (a) The melt index is 0.
50 weight of polypropylene resin within the range of 1-12
% And 90 wt% or less , and (b) 100 parts by weight of a resin component containing 10% by weight or more and less than 50% by weight of a polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst. After molding a polyolefin resin composition containing (2) 0.1 to 10 parts by weight of a polyfunctional monomer and (3) 1 to 50 parts by weight of an organic thermal decomposition type foaming agent into a predetermined shape,
A crosslinked polyolefin resin foam formed by crosslinking and foaming, wherein the polyethylene resin has a density of 0.860 to 0.950.
The width of the temperature at the time of elution of 10% by weight by the cross fractionation method from g / cm ³ to the temperature at the end of 100% by weight elution is 30 ° C. or less, and the value of the weight average molecular weight / number average molecular weight is 1 A cross-linked polyolefin resin foam characterized by having a size of 0.5 to 3.5. (1) (a) The melt index is 0.
50 weight of polypropylene resin within the range of 1-12
% And 90 wt% or less , and (b) 100 parts by weight of a resin component containing 10% by weight or more and less than 50% by weight of a polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst. After molding a polyolefin resin composition containing (2) 0.1 to 10 parts by weight of a polyfunctional monomer and (3) 1 to 50 parts by weight of an organic thermal decomposition type foaming agent into a predetermined shape,
A cross-linked polyolefin resin foam formed by cross-linking and foaming, wherein the polyethylene resin is a differential scanning calorimeter (DS).
The crosslinked polyolefin resin is characterized in that it has one crystal melting peak measured using C) and that the temperature range from the melting peak temperature to the end of melting of all crystals is within 20 ° C. Foam. 3. The polyethylene resin has one crystal melting peak measured using a differential scanning calorimeter (DSC), and the temperature range from the melting peak temperature to the end of melting of all crystals is 20. The crosslinked polyolefin-based resin foam according to claim 1, which has a temperature within the range of ° C.