JP2000007811A - Polypropylene-based resin composition for crosslinked foaming and its crosslinked foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide crosslinked foam excellent in heat resistance, moldability and pressure resistance while retaining perpendicular uniformity in quality by formulating to a resin composition a specific compound which is difficult to be influenced by the strength distribution of irradiating energy by ionizing radiation. SOLUTION: This polypropylene-based resin composition for foamingly crosslinking contains (A) 30-90 wt.% polyolefin-based resin having 0.5-5 g/(10 min) MFR(melt flow ratio), (B) 10-70 wt.% polyethylene-based resin having 1-20 g/(10 min) MFR, (C) 1-10 pts.wt. di(meth)acrylate compound of the formula [A is a CnH2n+1; B is a C2nH4n+1; X is H or CH3; (n) is 1-3] and (D) 1-10 pts.wt. thermally decomposable chemical foaming agent both based on 100 pts.wt. of the total quantity of the ingredients A and B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a crosslinked foamed polypropylene resin composition and a crosslinked foamed product thereof.
More specifically, a type that has excellent heat resistance and excellent workability to complex shapes, or high-temperature processing characteristics and pressure resistance, can handle a wide range of secondary processing, and can freely control flexibility etc. The present invention relates to a cross-linked foamed polypropylene resin composition suitable for continuously producing a foam and a cross-linked foam obtained by cross-linking and foaming the composition.

[0002]

2. Description of the Related Art Crosslinked foams using a polypropylene resin as a main component take advantage of their excellent moldability, cushioning properties, heat insulating properties and heat resistance, and are bonded to, for example, a PVC sheet or a TPO sheet for various processing. It is molded by the method and is used for interior materials such as car doors, instrument panels, console boxes, and seat back garnishes.

Conventionally, as one of the crosslinking methods in the production of a polyolefin resin foam, there is a method in which a foamable resin composition is formed into a continuous sheet and crosslinked by irradiation with ionizing radiation. This method is very effective when using an ethylene-based resin that is susceptible to cross-linking by irradiating radiation.However, when using a polypropylene-based resin that easily breaks molecular chains by irradiating radiation, In addition, it is difficult to provide crosslinking suitable for foaming because the resin deteriorates.

For this reason, when a polypropylene resin is used, JP-B-46-38716 and JP-A-61-69 are used.
No. 844 and JP-A-5-78514, a polyfunctional monomer having a reactive vinyl group, an acryl group and a methacryl group in a molecular structure is blended, and a polypropylene resin is deteriorated by irradiation with ionizing radiation. After crosslinking with irradiation energy of such a degree that no or only slight deterioration occurs, the foam is obtained by heating and foaming under normal pressure.

[0005]

However, conventional polyolefin resin foams cross-linked and foamed using a polyfunctional monomer may have various contents in the resin component depending on the type of the polyfunctional monomer and the mixing ratio of the resin. Since the compatibility with the resin is different, localization of the reactive monomer occurs as a result of poor dispersion, resulting in uneven crosslinking. This leads to irregularities in the stability and bubble diameter during foam production, destabilization of general mechanical properties, and a reduction in required workability and heat resistance. In addition, the cross-linking method using an electron beam has an energy distribution of an electron beam in the thickness direction of a sheet, that is, a distribution of a depth dose pattern, so that the irradiation energy and the reactivity of the polyfunctional monomer have a proportional relationship. Inevitably, a distribution of the degree of cross-linking occurs in the thickness direction of the sheet, and when a foam is formed, the shape of the cells has a distribution in the thickness direction of the foam, and therefore, a distribution also occurs in general physical properties. However, there is also a problem that the quality is reduced.

[0006] Recently, with the progress of the processing method, foams are required to have higher heat resistance and pressure resistance, and at the same time, to be flexible, contrary to these. To meet such demands, improvement of the resin composition itself is indispensable, but it is necessary to make the resin compositions corresponding to the required physical properties. For this reason, there has been a problem that the number of product types increases and production efficiency decreases, or process control and quality control become extremely complicated. Heretofore, a method has been adopted in which resin components having similar resin compositions are grouped and managed as much as possible, and characteristics are adjusted by adjusting the degree of crosslinking.

The inventors of the present invention have found that, among the limited resin composition ratios, the structure of the acrylate-based reactive monomer, which is generally considered to be poor in hydrolysis resistance and inferior in high-temperature physical properties, and the As a result of examining the relationship with the reactivity due to the linear energy, we found that one that reacts with a low electron beam energy, and therefore minimizes the energy dependence of the reaction, is able to reduce the distribution of the degree of crosslinking in the thickness direction of the foam. It is possible to obtain a polypropylene resin composition for cross-linking and foaming having excellent heat resistance, molding processability, and pressure resistance while maintaining a constant quality, which can be made almost constant.
The present invention has been reached.

[0008] That is, an object of the present invention is to eliminate the distribution of the degree of crosslinking in the thickness direction of the foam by adding a reactive monomer which is hardly affected by the intensity distribution of the irradiation energy of ionizing radiation. An object of the present invention is to provide a polypropylene-based resin composition for cross-linked foaming which is excellent in heat resistance, molding processability, and pressure resistance while maintaining quality, and a cross-linked foam thereof.

[0009]

In order to solve the above-mentioned problems, the polypropylene resin composition for cross-linking and foaming of the present invention comprises a polypropylene resin (a) having an MFR of 0.5 to 5 g / 10 min. 90% by weight and MFR 1-20g
1 to 10 parts by weight of a di (meth) acrylate compound (c) represented by the following general formula 2 with respect to 100 parts by weight of a total of 10 to 70% by weight of the polyethylene resin (b), It comprises a decomposition type chemical blowing agent in an amount of 1 to 10 parts by weight.

[0010]

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Further, the crosslinked polypropylene resin foam according to the present invention is obtained by molding the above polypropylene resin composition for crosslinking and foaming into a sheet, then irradiating it with ionizing radiation or irradiating ultraviolet rays to form a crosslinked resin. It consists of what was heated and foamed under pressure.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail. The polypropylene resin used in the present invention is not particularly limited, but is preferably propylene and ethylene or carbon which are polymerized by a gas phase method, a slurry method, a solution method, or the like using a Ziegler catalyst, a metallocene catalyst, or a heterogeneous catalyst. Α-olefin having a number of 4 to 12 copolymerized by 2 to 15% by weight and having a melting point of 125 to
155 ° C., MFR of 0.5 to 5 g / 10 min. In this copolymer, propylene may be copolymerized with ethylene or a monomer of an α-olefin having 4 to 12 carbon atoms, but in terms of mechanical strength and heat resistance, those having as large a carbon number as possible are used. preferable.

Ethylene or 4 to 4 carbon atoms to be copolymerized
The copolymerization amount of the α-olefin of No. 12 is preferably 2 to 15
%, More preferably 3 to 8% by weight. 2% by weight
When the value is less than the above, the crystallinity of the resin is increased, which is preferable in terms of heat resistance and mechanical strength. However, when the crystallinity is increased, the resin is hardened, the buffering property is deteriorated, and the impact resistance at a low temperature is lowered. In addition, when the resin is irradiated with ionizing radiation and crosslinked, it is difficult to control the degree of crosslinking even if a large amount of reactive monomer is added.
% Or more is not preferred. On the other hand, when it exceeds 15% by weight, it is preferable in terms of controlling crosslinking and flexibility, but it is not preferable because the melting point is lowered and heat resistance and pressure resistance at high temperatures are deteriorated.

The melting point of the polypropylene resin is preferably 125 to 155 ° C., more preferably 130 to 145 ° C.
It is. If the melting point is less than 125 ° C., it is not preferable because the application is restricted from the viewpoint of heat resistance.
When the temperature exceeds the above, it is preferable in that the melting point becomes higher, the heat resistance is improved, and it can be applied to a wide range of applications. However, it is not preferable because the shearing heat generated in the extrusion step at the time of forming the foaming sheet is increased, and the foaming agent is easily decomposed.

[0015] The MFR of the polypropylene resin is 0.5 to
5 g / 10 min, preferably 1 to 3 g / 10 min. M
When the FR is less than 0.5 g / 10 min, the foaming agent is decomposed due to the heat generated by shearing, and the irregularity of air bubbles tends to occur, which is not preferable. On the other hand, when the FR exceeds 5 g / 10 min, the melt viscosity becomes low, and the decomposition of the foaming agent is reduced. Although the irregularity of bubbles is suppressed and the irregularity of bubbles is eliminated, a smooth sheet cannot be obtained unless a special cooling device is used at the time of sheet molding, or the elongation of the foam decreases, the shape retention during heat molding deteriorates, the high temperature Is unfavorable because the pressure resistance becomes worse and a good molded product cannot be obtained.

The polyethylene resin used in the present invention is a copolymer of ethylene and an α-olefin having 4 to 12 carbon atoms using a Ziegler catalyst, a metallocene catalyst or the like to have a density of 0.890 to 0.940 g / cm ³ , MFR is 1-2
0 g / 10 min. Α copolymerized with ethylene
The type of olefin is not particularly limited as long as it is selected from among 4 to 12 carbon atoms, but is preferably 4 to 12 carbon atoms.
A copolymer of 8 is advantageous in terms of both price and physical properties. Density 0.890~0.940g / cm ^3, preferably 0.905~0.930g / cm ^3. A density of less than 0.890 g / cm ³ is preferred in terms of flexibility, but lowers the melting point and deteriorates the heat resistance, and the resin becomes sticky, resulting in poor mixing of the foaming agent or the like in the raw material mixing step. It is not preferable because it causes blocking of the foam. If the density exceeds 0.940 g / cm ³ , it is preferable in terms of mechanical strength, heat resistance and the like, but it is not preferable because the crystallinity becomes high and the film becomes hard and the buffering property decreases. MFR is 1 to 20 g / 10 min, preferably 3 to 10 g
g / 10 minutes. If the MFR is less than 1 g / 10 minutes, the melt viscosity of the resin becomes high, so that the foaming agent is decomposed due to heat generated by shearing during sheet molding, and coarse bubbles are easily generated, which is not preferable. On the other hand, if it exceeds 20 g / 10 min, the melt viscosity becomes low and the decomposition of the foaming agent is suppressed, so that it is preferable in terms of the generation of coarse bubbles, but a smooth sheet can be obtained unless a special cooling device is used during sheet forming. It is not preferable because the elongation of the foam is reduced or the elongation of the foam is reduced, so that the shape retention during the heat molding is deteriorated and a good molded product cannot be obtained.

The di (meth) acrylate compound represented by the following general formula 3 needs to be used in the present invention.

[0018]

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In the above compounds used in the present invention, n of A and B is 1 to 3, preferably 1. When n is 0, water resistance, that is, hydrolysis is liable to occur, so that high-temperature physical properties of the crosslinked and foamed product are deteriorated, and self-polymerization is liable to occur during storage. ,
The water resistance improves, and the stability during storage increases, but the electron beam energy required to cause a crosslinking reaction increases, and as a result, the irradiation energy dependence of the crosslinking reaction increases. Crosslink distribution in the vertical direction occurs, the solution viscosity of the compound itself increases, the mixing property with the resin powder and the blowing agent powder deteriorates when preparing the resin composition for foaming, and the aggregation of the foaming agent is promoted, resulting in This is not preferable because it may cause the generation of coarse bubbles. Further, X is preferably a methyl group (CH ₃ ). When H is used, it is not preferable because skin irritation (PII value) is increased and special consideration is required for the working environment of the worker.

In the present invention, the compound can be used by adsorbing it on a powder having porous pores so that the liquid can be handled as a powder. Examples of the powder having pores include, but are not limited to, silica gel fine powder, inorganic materials such as white carbon, and copolymers of acryl and vinyl chloride, and granular polyethylene powder. Not something. The amount by which the di (meth) acrylate compound used in the present invention is adsorbed in this way depends on the adsorptivity of the powder used.
It can be said that 80% by weight, preferably about 30 to 70% by weight is good. In other words, when the amount is less than 10% by weight, a high degree of cross-linking, specifically, when a degree of cross-linking exceeding 60% is obtained, the amount of the compound used in the present invention increases, so that the amount of powder is large. As a result, a decrease in the physical properties of the foam, specifically, elongation and a decrease in the moldability, are not preferred. On the other hand, adsorbing an amount of more than 80% by weight is preferable because the influence on the physical properties of the foam is eliminated, but it is not preferable because blocking easily occurs during storage, and conversely, handleability deteriorates.

The resin composition for a foam and the foam according to the present invention may contain 30 to 90% by weight, preferably 50 to 80% by weight of a polypropylene resin and 10 to 7% by weight of a polyethylene resin.
The di (meth) acrylate compound (c) represented by the above-mentioned general formula is added in an amount of 1 to 10 parts by weight, preferably 2 to 100 parts by weight of a mixture of 0% by weight, preferably 20 to 50% by weight.
７7 parts by weight. Crosslinked foam according to the present invention obtained from such a resin composition,
It is excellent in heat resistance, various moldability, elongation and flexibility, and is particularly suitable for molding under high temperature or high pressure molding (stamping, injection).

In the present invention, if the content of the polypropylene resin is less than 30% by weight, it is preferable in terms of flexibility when the foam is formed, but it is not preferable because the heat resistance is lowered.
Exceeding the weight percentage is preferable in terms of heat resistance, but is not preferable because it becomes hard and the buffering property deteriorates.

In the present invention, if the content of the polyethylene resin is less than 10% by weight, it is preferable from the viewpoint of heat resistance, but it is not preferable because the resin becomes hard and the buffering property deteriorates, and the heat moldability deteriorates. Although it is preferable in terms of cushioning property and moldability, it is not preferable because heat resistance deteriorates.

If the amount of the di (meth) acrylate compound according to the present invention is less than 1 part by weight, the amount of vinyl groups involved in crosslinking becomes insufficient, and it becomes impossible to set a wide range of crosslinking degree. When the amount exceeds the part, it is preferable in terms of setting the degree of crosslinking in a wide range, but since it is a liquid substance, the effect of a plasticizer in the extrusion step becomes excessive, and the molten state in the extruder becomes apparently low, so that it becomes difficult to extrude. Not preferred. Further, it is considered that the number of crosslinking points increases beyond the apparent degree of crosslinking, but it is not preferable because elongation is reduced and consequently moldability is reduced.

The thermal decomposition type chemical blowing agent used in the present invention includes azodicarbonamide, azodicarboxylic acid ester compound, azodicarboxylate, tetrazole compound,
N, N'-dinitrosopentamethylenetetramine or the like can be used. These may be used singly or as a mixture, or may be used in combination with a zinc compound, an amine compound, or the like to control foaming. The addition amount is preferably in the range of 1 to 20 parts by weight.

In the present invention, antioxidants represented by hindered phenols, thios, etc., processing stabilizers, flame retardants, inorganic fillers, pigments, etc. are added according to the purpose to obtain desired quality. It can be.

In the present invention, after the resin composition of the present invention is melt-extruded and formed into a sheet, it is necessary to carry out cross-linking at the stage of this sheet. Irradiating a line is industrially preferred. The irradiation energy is 0.5 to 20 Mrad
Is appropriate, but it is preferable to crosslink at a maximum of 10 Mrad or less. The crosslinking caused by the irradiation energy, that is, the gel fraction is 20 to 70%, and the gel fraction is 20%.
If it is less than 70%, the pressure resistance at high temperatures decreases, and press molding cannot be performed, which is not preferable. If it exceeds 70%, the pressure resistance improves but becomes hard, and the impact resistance at low temperatures deteriorates, and cracks are likely to occur. It is not preferable.

The foam of the present invention is produced by various foaming methods, specifically, a vertical (horizontal) type hot air foaming method, a method typified by a foaming method in a chemical solution bath, and the like. The foaming method is preferable because a foam having good physical properties in the sheet longitudinal direction (MD) and the width direction (TD) can be obtained.

Next, one embodiment of the polyolefin resin composition for crosslinking and foaming according to the present invention and a method for producing the crosslinked foam thereof will be described.

MFR obtained by random copolymerization of propylene with 4.2% by weight of ethylene has an MFR of 1.8 g / 10 minutes and a melting point of 13
MFR of 128 kg of 9 ° C. polypropylene resin powder and ethylene copolymerized with α-olefin having 6 carbon atoms is 8
g / 10 minutes, 32 kg of polyethylene resin powder having a melting point of 125 ° C., and “Irganox” 1010 as a stabilizer.
Azodicarbonamide 1 as a foaming agent
7.7 kg, 3.5 kg of a dimethacrylate compound in which n of A and B is 1 are prepared, and a polypropylene resin, a polyethylene resin, a foaming agent, and a stabilizer are charged into a Henschel mixer having an effective volume of 750 liters, and 200 ~ 400r
rpm for about 3 minutes, then 800-100
After high-speed rotation of 0 rpm and mixing for 3 minutes, a liquid dimethacrylate compound is added, and the mixture is further mixed for 3 minutes to obtain a foaming resin composition.

The foaming resin composition is introduced into a vented extruder heated to a temperature at which the foaming agent does not decompose, specifically, heated to 160 to 190 ° C., and extruded from a T-die.
It was formed into a crosslinked foaming sheet having a width of 75 mm and a width of 500 mm. The sheet is irradiated with a 5 Mrad electron beam to crosslink, and then continuously introduced into a foaming device on a chemical bath set at a temperature 20 to 50 ° C. higher than the decomposition temperature of the foaming agent, and heated and foamed to form a continuous sheet-like crosslink. Wound as a foam. The foam thus obtained had a thickness of 3.1 mm and a width of 1350.
mm, the degree of crosslinking was 55%, and the expansion ratio was 25 times.

As described above, in the present invention, the use of divinylbenzene as a crosslinking aid has been known, but the divinylbenzene has isomers and the mechanism involved in crosslinking of each structure is not known. Not, for example, p
If only the body is used, the crosslinkability is remarkably good, but the elongation of the foam is reduced, and it cannot be applied to various molding methods, or if only the m body is used, although the elongation of the foam is good, The disadvantage that a large amount of electron beam energy is required, or if these are mixed and used, such compounds are originally poorly compatible with polyolefin-based resins, so they are kneaded into the resin. However, there was a drawback that the cross-linking properties of the two could not be balanced and the cross-linking state became unstable. However, the use of an alkyl group-containing monofunctional vinyl compound compatible with both divinylbenzene and the polyolefin resin. It has been found that stabilization of crosslinkability can be obtained by the method. The crosslinked foam obtained from the resin composition according to the present invention has excellent heat resistance, various moldability, elongation, and flexibility, and is particularly suitable for molding under high temperature or high pressure molding (stamping, injection). It is.

[Evaluation Method and Evaluation Criteria] The evaluation method and evaluation criteria according to the present invention are as follows. (1) Degree of Crosslinking The foam is shredded and precisely weighed at 0.2 g. This was used as a solvent and extracted with xylene at a temperature of 100 ° C. for 8 hours using a Soxhlet extractor. The insolubles were taken out, washed with pure water, further washed with acetone, and further dried with a vacuum dryer heated to 80 ° C. After heating for 1 hour to completely remove volatile components, the mixture is naturally cooled at room temperature. The weight (W ₁ ) g of this product is measured, and the degree of crosslinking is determined by the following equation. Degree of crosslinking = (W ₁ /0.2)×100(%)

(2) Formability Heat-formed by a vacuum forming machine equipped with a cup-shaped forming die having a depth (L) with respect to the diameter (D), and the L-shaped formed into a cup without breaking the foam. The / D ratio is defined as moldability. Normally, molds of up to 1.0 are arranged side by side in L / D 0.2 increments, and the depth to which the mold is torn is observed. Measure moldability. L / D: Pass 0.5 or more

(3) Mechanical strength and elongation Measured according to JIS-K-6767. Mechanical strength passes (expansion ratio x (-1.5) + 45)) or more. Elongation passes 250% or more.

(4) Heat Resistance A 15 × 15 cm piece is cut out from the foam sheet, and measurement marks are drawn at intervals of 10 cm in the sheet longitudinal direction (MD) and width direction (TD), and the thickness (T) is measured. Place this sample on a heat-resistant plate on which calcium carbonate was sprayed.
Put in a hot air oven heated to 0 ° C., take out after heating for 2 hours, and cool naturally to room temperature. The mark interval (MDx, TDx, Tx) of this sample is measured, the dimensional change rate is calculated by the following equation, and the heat resistance is evaluated based on the following criteria. MD: ((100−MDx) / 100) × 100 (%) TD: ((100−TDx) / 100) × 100 (%) T: (((T−Tx) / T) × 100 (%) Heat resistance : MD and TD are acceptable within ± 5%. T is ±
Pass within 7%.

(5) Melting point scanning calorimeter (manufactured by PerkinElmer: DSCII)
The largest peak in the melting endothermic spectrum measured in I) is defined as the melting point.

(6) MFR The polypropylene resin was measured according to JIS-K-6758, and the polyethylene resin was measured according to JIS-K-6760.

(7) Density The polyethylene resin was measured according to JIS-K-6760.

[0040]

Next, the present invention will be described based on embodiments. Example 1 96 kg of polypropylene resin powder obtained by random copolymerization of propylene with 4.8% by weight of ethylene at a melting point of 141 ° C. and an MFR of 1.5 g / 10 min was mixed with α-olefin having 6 carbon atoms in ethylene. Polymerized density of 0.931 g / c
m ³ , MFR is 10.3 g / 10 min, melting point is 125 ° C., 64 kg of polyethylene resin powder, 0.7 kg of “Irganox” 1010 as a stabilizer, 7.4 kg of azodicarbonamide as a foaming agent, In the formula, A
Prepare 3.2 kg of a dimethacrylate compound of の CH ₃ , B ＝ C ₂ H ₅ , XＣＨCH ₃ , and add a polypropylene resin, a polyethylene resin, a foaming agent, and a stabilizer to an effective volume of 7 kg.
Put into a 50 liter Henschel mixer,
Mix at low speed of 400 rpm for about 3 minutes, then 800
After high-speed rotation of about 1000 rpm and mixing for 3 minutes, a liquid dimethacrylate compound is added, and the mixture is further mixed for 3 minutes to obtain a foaming resin composition.

The foaming resin composition is introduced into a vented extruder heated to a temperature at which the foaming agent does not decompose, specifically, heated to 160 to 190 ° C., extruded from a T-die, and has a thickness of 2.00 mm and a width of 640 mm. Into a sheet for crosslinking and foaming. The sheet is irradiated with a 4 Mrad electron beam to crosslink, and then continuously introduced into a vertical hot air foaming apparatus set at a temperature 40 ° C. higher than the decomposition temperature of the foaming agent, and subjected to heat foaming to form a continuous sheet-like crosslinked foaming. Wound as a body.

The foam thus obtained had a thickness of 4.0 mm, a width of 1400 mm, a degree of crosslinking of 52%, and an expansion ratio of 18 times. Table 1 shows the composition and production conditions of this product, and Table 2 shows the characteristics of the product.

Comparative Example 1 A crosslinked foam was prepared using a resin composition shown in Table 1 and the properties of the obtained foam are shown in Table 2.

[0044]

[Table 1]

[0045]

[Table 2]

As described above, the crosslinked foam obtained from the resin composition according to the present invention shown in Example 1 has excellent heat resistance, various moldability, elongation and flexibility, and particularly high-pressure molding under high temperature. (Stamping, injection).

On the other hand, what was shown in Comparative Example 1 was an unsatisfactory crosslinked foam having insufficient elongation, moldability or heat resistance because it was outside the scope of the present invention.

[0048]

As described above, according to the polypropylene resin composition for cross-linking and foaming and the cross-linked foam of the present invention, the resin composition is hardly affected by the intensity distribution of irradiation energy of ionizing radiation. Because a specific compound is blended, while maintaining a certain quality, especially in the thickness direction,
A crosslinked foam having excellent heat resistance, moldability and pressure resistance can be obtained.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaru Morie 1-1-1 Sonoyama, Otsu-shi, Shiga F-term in the Toga Company's Shiga Plant (reference) 4F074 AA18 AA24 AA48M AA98 AB05 BA12 BA13 BB03 BB25 CA25 CA29 CA34 CC04Y CC06X CC32Y DA02 DA04 DA08 DA35 4J002 BB05X BB14W BB15W BB15X EH076 EQ017 EQ037 ES007 EU007 FB296 FD146 FD327 GN00 4J011 QA13 RA10 TA08 TA10 UA03 VA04 WA07

Claims (4)

[Claims] 1. A polypropylene-based resin (a) having an MFR of 0.5 to 5 g / 10 min. And a polyethylene-based resin (b) having an MFR of 1 to 20 g / 10 min.
With respect to 100 parts by weight of 0 to 70% by weight, the following general formula 1 is used. The di (meth) acrylate compound (c) represented by
A polypropylene resin composition for cross-linking and foaming comprising 10 parts by weight and 1 to 10 parts by weight of a thermal decomposition type chemical foaming agent. 2. The di (meth) acrylate compound is used in an amount of 10 to 80% by weight based on a powder having a porous pore structure.
The polypropylene resin composition for cross-linking and foaming according to claim 1, wherein the adsorbed one is used. 3. A crosslinked polypropylene resin foam formed by molding the polypropylene resin composition for crosslinking and foaming according to claim 1 or 2 into a sheet, irradiating it with ionizing radiation, and then heating and foaming under normal pressure. body. 4. The gel fraction according to claim 3, wherein the gel fraction is 20 to 70%.
The crosslinked polypropylene-based resin foam according to the above.