JPH08231747A - Foam sheet of polypropylene resin composition - Google Patents

Abstract

PURPOSE: To provide a thin sheet having a high expansion ratio, maintaining characteristic heat resistance of polypropylene or excellent heat insulating properties and cushioning properties. CONSTITUTION: This foam sheet of a polypropylene resin composition having 0.1-0.5g/cm<3> density, 1-15mm thickness and 3-9 times foaming ratio is obtained by extruding and expanding 100 pts.wt. of a polypropylene resin composition comprising 5-70wt.% syndiotactic polypropylene having >=0.5 syndiotactic pendant ratio measured by<13> C-NMR and 95-30wt.% of an isotactic polypropylene having >=0.90 isotactic pendant ratio measured by<13> C-NMR and 2-50 pts.wt. of a resin composition containing an endothermic blowing agent starting decomposition reaction at >=160 deg.C from an extruder with the tip part (die or head) of the extruder set at 160 deg.C into the atmosphere.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a foamed sheet of a polypropylene resin composition.

[0002]

2. Description of the Related Art Foamed sheets made mainly of polypropylene resin are widely used, for example, as food containers and interior materials for automobiles. However, this foamed sheet has a low foaming ratio, so that there are problems such as insufficient heat insulating property and poor buffering property. Further, when an extruded foam sheet having an expansion ratio of 3 times or more is to be obtained, the thickness of the foam sheet is limited to about 3 mm, which makes it difficult to produce a thin extruded foam sheet. Therefore, for example, when it is used as a packaging material, it lacks flexibility. On the other hand, in recent years, J.
A. It was discovered by Ewen et al. That polypropylene having a high tacticity such that the syndiotactic pentad fraction exceeds 0.5 can be obtained by using a transition metal catalyst having an asymmetric ligand and a catalyst comprising aluminoxane (J Am. Chem. Soc., 1988, 1
10, 6255-6256) The possibility of new polypropylene is expected.

[0003]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above problems and to provide a polypropylene resin composition which is thin and has a high expansion ratio and which has heat insulation and cushioning properties in addition to the heat resistance originally possessed by polypropylene. To provide a foamed sheet of a product.

[0004]

In view of the above problems, the inventors of the present invention have made extensive studies on the foamed sheet of the polypropylene resin composition, and as a result, the present invention has been achieved. That, ¹³ C-NMR syndiotactic polypropylene 5-70 wt% syndiotactic pentad fraction measured is 0.5 or more by, ¹³ C-NMR isotactic pentad fraction measured by the Isotactic polypropylene 9 of 0.90 or more
Polypropylene resin composition 10 comprising 5 to 30% by weight
2 parts by weight to 50 parts by weight of a resin composition containing 0 part by weight and an endothermic foaming agent that starts a decomposition reaction at 160 ° C. or higher is introduced from the inside of the extruder where the temperature of the extruder tip (die, head) is set to 160 ° C. Density 0.1 to be obtained by extrusion foaming in the air
0.5 g / cm ³ , thickness 1 to 15 mm, foaming ratio 3 to 9
Double polypropylene resin composition foam sheet.
Hereinafter, the present invention will be described in detail.

The syndiotactic polypropylene used in the present invention may be syndiotactic homopolypropylene or syndiotactic polypropylene copolymer which is a copolymer of propylene and α-olefin. The syndiotactic pentad fraction determined by ¹³ C-NMR is 0.5 or more in the case of syndiotactic homopolypropylene,
0.7 or more is preferable and 0.75 or more is especially preferable.
In the case of a syndiotactic polypropylene copolymer, the syndiotactic pentad fraction of the propylene chain is 0.3 or more, preferably 0.5 or more,
0.7 or more is particularly preferable.

The comonomer used in the syndiotactic polypropylene copolymer used in the present invention is preferably an α-olefin other than propylene. α-
Examples of the olefin include ethylene, 1-butene, and 3
-Methyl-1-butene, 1-hexene, vinylcyclohexene, 1-decene, 1-hexadecene, cyclopentene, olefins such as norbornene, hexadiene, octadiene, decadiene, dicyclopentadiene, 5-
Examples thereof include copolymers containing dienes such as ethylidene 2-norbornene. Such a copolymer is preferably obtained by copolymerizing propylene and a comonomer in the presence of a known catalyst capable of giving a poly-α-olefin having good syndiotacticity.
The comonomer content varies depending on the comonomer and cannot be specified, but is usually 1 to 30% by weight, preferably 5 to 1
It is 5% by weight. The molecular weight of syndiotactic polypropylene is 0.1 to 10 dl / g, preferably 0.5 as the intrinsic viscosity measured in a tetralin solution at 135 ° C.
˜5.0 dl / g.

The catalyst for producing syndiotactic polypropylene in the present invention is, for example, JP-A-2-4.
No. 1303, No. 2-41305, No. 2-274703, No. 2-274704, No. 3-179005, No. 3-17900.
Examples of the catalyst include a bridged transition metal compound having mutually asymmetric ligands and a cocatalyst as described in JP-A-6-69394 and JP-A-4-69394, but catalysts having different structures. However, any polypropylene can be used as long as it can produce polypropylene having a syndiotactic pentad fraction of 0.5 or more as measured by ¹³ C-NMR, and the polymerization method can be a slurry polymerization method, a bulk polymerization method, a gas polymerization method. Any of the phase polymerization methods can be used.

In the present invention, it is excellent in heat resistance and buffering property,
In order to improve the expansion ratio, syndiotactic polypropylene is mixed with isotactic polypropylene having an isotactic pentad fraction of 0.90 or more determined by ¹³ C-NMR. Especially the mixing ratio is
Syndiotactic polypropylene is 5 to 70% by weight, preferably 20 to 60% by weight, 30 to 50% by weight
Is more preferable. The isotactic polypropylene content is 95 to 30% by weight, preferably 80 to 40% by weight, and more preferably 70 to 50% by weight. If the syndiotactic polypropylene content exceeds 70% by weight, the solidification rate will decrease during extrusion foaming, so that a foamed sheet having a sufficient expansion ratio may not be obtained. Since the solidification rate is improved, a foamed sheet having a sufficient expansion ratio may not be obtained.

The isotactic pentad fraction determined by ¹³ C-NMR of isotactic polypropylene, which is important in the present invention, is 0.90 or more in order to obtain a sufficient expansion ratio as an extrusion foam sheet. It is necessary, and preferably 0.95 or more, particularly 0.97 or more. Isotactic polypropylene is
It may be isotactic homopolypropylene or an isotactic polypropylene copolymer which is a copolymer of propylene and α-olefin, and known isotactic polypropylene that is commercially available can be used.

Examples of the α-olefin which is a comonomer used in the isotactic polypropylene copolymer used in the present invention include ethylene, 1-butene, 3-methyl-1-butene, 1-hexene, vinylcyclohexene and 1-decene. Preferred are olefins such as 1-hexadecene, cyclopentene and norbornene, and dienes such as hexadiene, octadiene, decadiene, dicyclopentadiene and 5-ethylidene-2-norbornene. Such a copolymer can be obtained by copolymerizing propylene and a comonomer in the presence of a known catalyst capable of giving a poly-α-olefin having good isotacticity. The comonomer content is not particularly limited, but is preferably 0.1 to 10% by weight, more preferably 0.3 to 5% by weight.

The melt flow index of isotactic polypropylene (230 ° C., 2.16 kg load, hereinafter referred to as MFI) is 0.1 to 40 g / 10 m.
In is preferable, and 5 to 20 g / 10 min is preferable. If the MFI of the isotactic polypropylene is less than 0.1 g / 10 min, the fluidity may be low, which may cause difficulty in compounding, and the MFI of 40 g / 1.
If it exceeds 0 min, a sufficient expansion ratio as a foam-molded product obtained as a product may not be obtained.

In the polypropylene resin composition of the present invention, if necessary, an antiblocking agent, a lubricant, a crystal nucleating agent, an ultraviolet absorber, a heat stabilizer, a weather resistance stabilizer, a radiation resistance agent, a pigment,
It is preferable to add an additive such as a dye. As the method for producing the polypropylene resin composition of the present invention, syndiotactic polypropylene, isotactic polypropylene and, if necessary, known stabilizers and additives are mixed in a mixer such as a Henschel mixer, and then in an extruder. It can be produced by a method of melt kneading or granulation, or a method of melt kneading with a roll, a Banbury mixer, a pressure kneader, a Brabender or the like. Further, syndiotactic polypropylene and isotactic polypropylene may be individually granulated by an extruder or the like, and may be blended and used when extrusion-foaming.

The resin composition containing an endothermic foaming agent (hereinafter abbreviated as a foaming agent masterbatch) used in the present invention means 1 to 1 parts of the endothermic foaming agent with respect to 100 parts by weight of the resin.
It can be easily produced by blending 100 parts by weight and melt-kneading using a known machine such as a pressure kneader, a Banbury mixer, a single-screw extruder or a twin-screw extruder. The melt-kneading temperature is set to 160 in consideration of the decomposition start temperature of the endothermic foaming agent.
It is preferably produced at a temperature of not higher than 0 ° C. The resin used in the blowing agent masterbatch of the present invention has a melt flow index (230 ° C., 2.16 kg load, hereinafter referred to as MI) of 2 g / 10 minutes or more, preferably 10 g / 10 minutes or more, and particularly preferably 20 g. / 10 minutes or more is recommended. If the MI is less than 2 g / 10 minutes, the fluidity may be low, and mixing may be difficult. Further, the higher the MI, the better the dispersed state of the foaming agent.

As the kind of resin, propylene homopolymer, copolymer of propylene and α-olefin, for example, propylene-ethylene copolymer, propylene-butene copolymer, propylene-ethylene-butene terpolymer. Can be used. Further, ethylene-butene copolymer, low density polyethylene, high density polyethylene, linear low density polyethylene, ultra low density polyethylene, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer,
Styrene-butadiene block copolymer, styrene-butadiene-styrene triblock copolymer, styrene-
Examples thereof include isoprene-diblock copolymer, styrene-isoprene-styrene triblock copolymer, polybutene and the like. Further, in order to adjust the MI, a polypropylene resin which has been previously heat-degraded by adding an organic peroxide may be used.

The endothermic foaming agent used in the foaming agent masterbatch of the present invention is, for example, a mixture of polycarboxylic acid and an inorganic carbonic acid compound, and monoglyceride and stearic acid are used in order to prevent the adsorption of water on the surface thereof. ,
Those treated with a silane compound (such as a silane coupling agent) are also included. Here, as the polycarboxylic acid, saturated dicarboxylic acids such as citric acid, fumaric acid and tartaric acid, unsaturated dicarboxylic acids, and salts thereof with Ca, Mg, Na and the like, sodium citrate hydride, citric acid 1 Sodium and the like are also included. Inorganic carbonate compounds include alkali metal and alkaline earth metal carbonate compounds such as sodium aluminum bicarbonate, sodium bicarbonate, and the like, and mixtures thereof. The endothermic foaming agent is not limited to these, and includes all those having a decomposition temperature higher than 160 ° C.

The blowing agent masterbatch used in the present invention is added in an amount of 2 to 50 parts by weight, preferably 5 to 20 parts by weight, based on 100 parts by weight of the polypropylene resin composition. When it is less than 2 parts by weight, the effect of reducing flexibility and weight is small, and when it exceeds 50 parts by weight, the surface appearance of the product may be rough. In the method of the present invention, the polypropylene resin composition and the blowing agent masterbatch are extruded and foamed from the inside of the extruder into the atmosphere to obtain a foamed sheet, and the foamed sheet has a density of 0.1 to 0.5 g / c
m ³ , thickness 1 to 15 mm, and expansion ratio 3 to 9 times.

By setting the density, thickness and expansion ratio of the foamed sheet within the above ranges, the use of a specific amount of syndiotactic polypropylene and isotactic polypropylene can prevent the generation of corrugate. Even if a large amount of a foaming agent is added, the brittleness of the foamed sheet is improved, the moldability is improved, and the appearance such as smoothness is also improved. Furthermore, as a result of good compatibility between the foaming agent and the polypropylene resin composition, stable extrusion foaming is possible and fluctuations in the foaming ratio are reduced. Regarding the set temperature of the extruder, the extruder tip (die, head) is set to 15
A good foamed sheet with a good appearance and a high expansion ratio when the temperature of the extruder tip (die, head) is set below the temperature of the cylinder, such as 5 ° C to 180 ° C and the cylinder 180 ° C to 230 ° C. Is preferable, because

The density of the foamed sheet can be easily adjusted by a combination of the composition ratio of the polypropylene resin composition, the type of the foaming agent, the addition amount and the like. Also,
The thickness of the foamed sheet is determined by adjusting the interrelationship between the discharge rate of the extruder and the take-up speed of the extruded foamed sheet.
Further, the expansion ratio of the foam sheet is adjusted by a combination of the composition ratio of the polypropylene resin composition, the type of the foaming agent, the addition amount, and the like. In the present invention, it is preferable to add a small amount of an inorganic substance such as talc, silica gel, calcium carbonate or a chemical foaming agent as a foaming cell regulator.

As a method for obtaining a foamed sheet, a conventional T
Using a die extruder, inside the extruder, syndiotactic polypropylene, isotactic polypropylene (previously,
It may be granulated by a known kneader such as a single-screw extruder or a twin-screw extruder. ) And a blowing agent masterbatch are blended and extruded through a T die at the tip of the extruder and brought into contact with a cooling roll to obtain a foam sheet, or extruded from a circular die at the tip of the extruder. A method may be employed in which a tube-shaped foam is obtained by foaming and then the tube-shaped foam is cut open along the extrusion direction to obtain a foam sheet.

[0020]

EXAMPLES The following examples are provided for illustrating the present invention further in detail, but the present invention is not limited thereto. The measuring methods in Examples are as follows, and the measured values are shown in Tables 1 and 2. (1) Melt flow index: ASTM D-12
38 (2) Density: ASTM D-1505 (3) Foaming ratio: Density of non-foamed sheet / Density of foamed sheet (4) Appearance: ◯: Corrugates and wrinkles are formed on the surface of the foamed sheet. Not observed, smoothness is good. Δ: Some wrinkles are seen on the surface of the foamed sheet, but smoothness is good. ×: Corrugates and wrinkles are seen on the surface of the foamed sheet. Poor smoothness

Examples 1 to 6 Syndiotactic polypropylene homopolymer [manufactured by Mitsui Toatsu Chemicals, Inc., SPP-1: MFI 3.2 g / 10
min, syndiotactic pentad fraction 0.787 measured by ¹³ C-NMR, intrinsic viscosity 1.39 measured in a tetralin solution at 135 ° C., crystallization temperature 74 measured by a differential scanning calorimeter. .6 ° C.], and according to the composition of Table 1, an isotactic polypropylene homopolymer [manufactured by Mitsui Toatsu Chemicals, Inc., J3H (SOL): M].
FI ¹³ g / 10 min, isotactic pentad fraction measured by ¹³ C-NMR 0.975], talc [Asada Flour Milling Co., JA-13R], known stabilizers [Shell Chemical Co., Ltd.]: B. H. T. , Ciba Gaigi
Co., Ltd .: Irganox 1010, calcium stearate (St-Ca)] is melt-kneaded with a twin-screw extruder to obtain pellets, and then a foaming agent master batch [manufactured by Eiwa Kasei Co., Ltd., EE-106]. : Decomposition start temperature of the contained endothermic foaming agent is 168 ° C.], and a T-die mold setting temperature is 160 ° C. and a cooling roll temperature is 75 using a 30 mmφ T-die extruder.
Extrusion foaming was performed at ℃ and a take-up speed of 2 m / sec.

Comparative Example 1 Isotactic ethylene-propylene random copolymer [MJS-G: MFI1.5 manufactured by Mitsui Toatsu Chemicals, Inc.]
g / 10 min, ethylene content 2.6% by weight] 100
Wt%, 1 part by weight of talc (JA-13R), and a known stabilizer are melt-kneaded in a twin-screw extruder to obtain pellets, and then the blowing agent master-batch (EE-106) is blended to obtain 3
0mmφ T die extruder set T die temperature 160
℃, cooling roll temperature 75 ℃, take-up speed 2m / sec
Was extruded and foamed.

Comparative Example 2 Isotactic ethylene-propylene block copolymer [BJS-G: MFI1.5 manufactured by Mitsui Toatsu Chemicals, Inc.]
g / 10 min, ethylene content 18% by weight] 100% by weight, talc (JA-13R) 1 part by weight, and a known stabilizer were melt-kneaded by a twin-screw extruder to obtain pellets, and then a blowing agent master- Blend the batch (EE-106) to 30
mmφ T die extruder with T die set temperature 160 ° C,
Extrusion foaming was performed at a cooling roll temperature of 75 ° C. and a take-up speed of 2 m / sec.

Comparative Example 3 Isotactic propylene homopolymer [EB-G: MFI 1.5 g / 10 min, manufactured by Mitsui Toatsu Chemicals, Inc.]
100 wt%, 1 part by weight of talc (JA-13R), and a known stabilizer were melt-kneaded in a twin-screw extruder to obtain pellets, and then a foaming agent master-batch (EE-106) was blended to obtain 30 mmφT. Set the die temperature of T-die by die extruder 1
60 ° C, cooling roll temperature 75 ° C, take-up speed 2m / s
Extrusion foaming was performed with ec.

Comparative Example 4 Syndiotactic propylene homopolymer (SPP-
1) 100% by weight, 1 part by weight of talc (JA-13R),
A known stabilizer was melt-kneaded with a twin-screw extruder to obtain pellets, and then a foaming agent master-batch (EE-106) was blended, and a T-die mold setting temperature of 160 ° C. was set with a 30 mmφ T-die extruder. Cooling roll temperature 75 ℃, take-up speed 2m
Extrusion foaming was performed at / sec.

Comparative Examples 5 and 6 Syndiotactic polypropylene homopolymer (SP
P-1) was melt-kneaded with isotactic polypropylene homopolymer [J3H (SOL)], talc (JA-13R), and a known stabilizer in a twin-screw extruder according to the composition shown in Table 3 to form pellets. After obtained, the blowing agent master-batch (EE-106) was blended, and the T-die mold setting temperature was 160 ° C and the cooling roll temperature was 7 using a 30 mmφ T-die extruder.
Extrusion foaming was performed at 5 ° C. and a take-up speed of 2 m / sec.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

The foamed sheet of the polypropylene resin composition of the present invention is a thin foamed sheet having a large expansion ratio, which maintains the original heat resistance of polypropylene and imparts heat insulating property and cushioning property. The foamed sheet. For example, the foamed sheet obtained by the present invention is processed into containers of various shapes by vacuum or pressure molding, packaging materials and interior materials of automobiles, and heat resistance,
It is suitable for use in products that make good use of heat insulating properties and cushioning properties.

Claims (1)

[Claims] 1. 5 to 70% by weight of syndiotactic polypropylene having a syndiotactic pentad fraction of 0.5 or more as measured by ¹³ C-NMR, ¹³ C-N
100 parts by weight of a polypropylene resin composition consisting of 95 to 30% by weight of isotactic polypropylene having an isotactic pentad fraction of 0.90 or more measured by MR, and an endothermic type that starts a decomposition reaction at 160 ° C. or more A resin composition containing 2 to 50 parts by weight of a foaming agent is extruded and foamed into the atmosphere from the inside of the extruder in which the temperature of the extruder tip (die, head) is set to 160 ° C., and the density is 0.1.
~ 0.5 g / cm ³ , thickness 1 to 15 mm, foaming ratio 3 to
A foam sheet of 9 times the polypropylene resin composition.