JPH08259721A - Modified polypropylene resin foam, multilayer foam, and molded article obtained therefrom - Google Patents

Abstract

PURPOSE: To improve the heat resistance, heat-insulating properties, chemical resistance, and impact resistance in refrigeration and transport by mixing a base resin with an ethylene/butene random copolymer. CONSTITUTION: Up to 98 wt.% base resin consisting of either a propylene homopolymer which gives, upon analysis by gel permeation chromatography (GPC), a camel-shaped mol.wt. distribution curve showing the presence of branched polymers in a high-mol. region and has a Z-average mol.wt. of 2.0×10<6> or higher and an MZ/MW (weight-average mol.wt.) ratio of 3.0 or higher, or an ethylene/propylene copolymer based on the propylene homopolymer and having an ethylene content of 1-10wt.%, is compounded with 2-40wt.% modifier consisting of an ethylene/butene random copolymer having a butene content of 5-30wt.% and a density of 0.86-0.92g/cm<3> optionally together with a small amount of an elastomer, e.g. a polyethylene resin, and further with an inorganic filler in an amount of 10-50wt.% based on all resins. The compound is fed to an extrusion foaming machine and a foaming agent is added thereto. The resulting mixture is thermally melted and extruded with a die.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modified polypropylene resin foam, a laminated foam and a molded article obtained from them. More specifically, the present invention provides a modified polypropylene resin foam, a laminated foam, and a modified polypropylene resin foam which can be used for heating in a microwave oven or the like and which does not crack even when used for storage and transportation at low temperature. Related to molded articles. Further, the modified polypropylene resin foam of the present invention,
Laminated foams and molded articles obtained from them are packaging materials,
It can be used for heat insulation and structural materials.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
As a food container that can be used for cooking in a microwave oven, a molded product made of polypropylene foam is used. This molded article is excellent in heat resistance, heat insulation, and chemical resistance, and thus is excellent as a food container and very useful. However, the glass transition point is generally around 0 ° C., and there is a problem that the glass breaks when used for freezing in an atmosphere of −30 ° C.

To improve the impact strength at low temperatures, a method of using a copolymer of propylene and ethylene, a method of mixing polyethylene resin, a method of mixing various rubber resins or elastomers with polypropylene resin, ethylene-propylene There is a method of mixing rubber and polyethylene resin. However, none of the methods sufficiently satisfy the requirements for food containers.

More specifically, the method using a copolymer of propylene and ethylene is more excellent in impact resistance at room temperature than the method using a propylene homopolymer. However, the impact resistance at low temperature of both these methods was slightly different. It is known that a method of mixing a polyethylene resin can obtain a foam having improved flexibility (Japanese Patent Application No. 6-260676). However, this method improved flexibility but had little effect on impact resistance.

Examples of the rubber-based resin used in the method of mixing various rubber-based resins include propylene-ethylene rubber which is often used for improving the impact resistance of polypropylene-based resins. When this propylene-ethylene rubber is mixed, in order to impart impact properties at a low temperature, it is necessary to add at least 20 to the polypropylene resin.
It is necessary to add more than weight%.

When this method is used in a non-foaming process, extrusion molding is generally carried out at a temperature of several tens of degrees Celsius higher than the melting point of the polypropylene resin. Therefore, the propylene-ethylene rubber can be mixed in a wide range with respect to the polypropylene resin. However, in the case of having a foaming step, it is necessary to apply sufficient tension to the resin in order to prevent the bubble from breaking during bubble growth. Therefore, it is necessary to lower the temperature of the resin to near the melting point. In addition, as a polypropylene resin, a resin having low fluidity is generally used, so that a mixed state with other resins is deteriorated. As a result, only foams with high open cell density and high density or foams with poor surface smoothness can be obtained, so the amount of rubber resin mixed is limited to a very small amount, and as a result, sufficient low temperature impact resistance is obtained. Could not be given.

Further, JP-A-6-212007 discloses a polypropylene block copolymer comprising polypropylene and an ethylene / α-olefin copolymer, an ethylene / α-olefin copolymer, and optionally a high density. A polypropylene-based foamed sheet using polyethylene as a base resin is described. In this publication, it is aimed to obtain a polypropylene-based foam sheet having excellent impact resistance,
The example describes a polypropylene block copolymer containing an ethylene / propylene copolymer, an ethylene / 1-butene copolymer, and a foamed sheet optionally using polyethylene. However, the inventors of the present invention have found that the polypropylene-based foamed sheet described in this publication does not have sufficient impact resistance at low temperatures.

In view of the above problems, the inventors of the present invention have
As a result of diligent study, it has excellent heat resistance, heat insulation and chemical resistance,
No cracking occurs during freezing storage and transportation especially at low temperature,
The inventors have found a modified polypropylene-based resin foam excellent in impact resistance, a laminated foam, and a molded product obtained from them, and arrived at the present invention.

[0009]

Thus, according to the present invention, it is a foam of a mixture obtained by mixing 2% by weight or more of an ethylene-butene random copolymer with a polypropylene resin as a base resin. Provided is a modified propylene resin foam. Further, according to the present invention, on at least one surface of the modified propylene resin foam, a propylene homopolymer, an ethylene-propylene copolymer, a high density polyethylene, a low density polyethylene, a linear low density polyethylene, a straight chain Provided is a laminated foam in which sheets made of any one of chain-like ultra-low density polyethylene, ethylene-propylene rubber, and ethylene-butene random copolymer or a mixture thereof are laminated.

Further, according to the present invention, there is provided a molded article comprising the modified propylene resin foam and the laminated foam. Next, the polypropylene resin that can be used as the base resin in the present invention is not particularly limited, and any known resin can be used. Among known resins, the Z-average molecular weight Mz is at least 2.0 × 10 ⁶ or more, the Mz / Mw (weight average molecular weight) is 3.0 or more, and a curve showing that the polymer contains a branched polymer A propylene homopolymer (referred to as a camel-type polypropylene resin) having an overhanging camel-type molecular weight distribution curve (according to gel permeation chromatograph) can be preferably used in the present invention. It is also possible to use a copolymer of ethylene and propylene containing 1 to 10% by weight of ethylene in the propylene homopolymer. This copolymer includes both block copolymers and random copolymers.

In the above resin, the Z average molecular weight Mz is
It is the average molecular weight that emphasizes the distribution on the highest molecular weight side as measured by gel permeation chromatography (hereinafter referred to as GPC), and means the average value of the cube of the molecular weight. Further, the weight average molecular weight Mw is an average molecular weight obtained when the measured physical property value is directly related to the weight of the polymer by measurement by GPC, and is 2 of the molecular weight.
It means the average value of the powers. The GPC conducted in the present invention
The measurement method of is as follows.

Measuring apparatus: GPC 150-C type (manufactured by Water) Measuring condition: column KF-80M (manufactured by SHODEX)
Column temperature 145 ° C (polypropylene resin, P
P) Injection temperature 145 ° C. Pump temperature 60 ° C. Sensitivity 32 Solvent used o-dichlorobenzene (1.0 ml / min) Scanning time 50 minutes Injection volume 400 μl If such polypropylene resin is used, sufficient melt tension at the time of foaming is obtained. And a foam having a desired density can be obtained.

Further, the polypropylene resin has a camel-type molecular weight distribution curve. The camel-type molecular weight distribution curve is, for example, a high molecular weight region as shown in FIG. It means a molecular weight distribution curve having a shape with a protrusion. The molecular weight distribution curve shows that certain components in the high molecular weight region have many branches. In addition, in FIG. 1, a curve A shows a camel-type polypropylene resin, and a curve B shows other polypropylene resins.

The polypropylene resin which can be used in the present invention includes MH-8 manufactured by Mitsubishi Chemical Co., Ltd. and A manufactured by Sumitomo Chemical Co., Ltd.
D571, S-131, etc. are mentioned. Further, the camel type polypropylene resin is specifically, X-10005, PF-814, SD-632, X11 manufactured by Highmont Co., Ltd.
277-22-1 and the like. In addition, PF-81
4, X-10005 is a propylene homopolymer, S
D-632 and X11277-22-1 are propylene-ethylene block copolymers.

2% by weight or more of an ethylene-butene random copolymer is mixed with the base resin as a modifier.
The ethylene-butene random copolymer usable in the present invention has a butene content of 5 to 30% by weight and a density of 0.8.
It is preferably 6 to 0.92 g / cm ² . In particular, the butene content is 10 to 25% by weight and the density is 0.87 to 0.90.
It is preferably g / cm ² .

Specific examples of the ethylene-butene random copolymer satisfying the above conditions are NO416 (butene content 22% by weight) and NO372 (butene content 1 manufactured by Sumitomo Chemical Co., Ltd.).
3% by weight) and the like. The modified polypropylene resin foam of the present invention contains 98% by weight of polypropylene resin.
Below, preferably 98 to 60 wt%, ethylene-butene random copolymer 2 wt% or more, preferably 2 to 40
Contains by weight percent. Here, if the polypropylene-based resin is more than 98% by weight, the effect of improving low temperature impact resistance is small, and if it is less than 60% by weight, the strength of the foam is lowered, which is not preferable. Further, if the content of the ethylene-butene random copolymer is more than 40% by weight, the strength of the foam will be deteriorated, which is not preferable, and if it is less than 2% by weight, there is no effect of improving low temperature impact resistance.

The modified polypropylene resin foam of the present invention contains a polyethylene resin, an α-olefin polymer, an ionomer, and ethylene-ethylene resin within a range that does not impair physical properties such as foamability, heat resistance and impact resistance. Propylene rubber (E
A small amount of elastomer such as P rubber may be mixed. Further, an inorganic filler may be added to the base resin in an amount of 10 to 50% by weight based on the total amount of the resin in order to improve strength and durability and increase the amount. As inorganic fillers that can be used,
Although not particularly limited, silica, alumina, titanium oxide,
Examples include talc, clay, calcium carbonate and the like.

The modified polypropylene resin foam of the present invention preferably has a density of 0.6 to 0.02 g / cm ³ , and more preferably 0.6 to 0.06 g / cm ³ . Here, if the density is larger than 0.6 g / cm ³ , the heat insulating property becomes poor, which is not preferable. The shape of the modified polypropylene resin foam is not particularly limited and may be a sheet plate or a tube. When formed into a sheet plate, its thickness is usually 0.5 to 4.0 mm.

Further, in the present invention, a propylene homopolymer, an ethylene-propylene copolymer, a high density polyethylene, a low density polyethylene, a linear low density polyethylene, a straight chain low density polyethylene There is also provided a laminated foam in which sheets made of any one of chain-like ultra-low density polyethylene, ethylene-propylene rubber, and ethylene-butene random copolymer or a mixture thereof are laminated. The sheet laminated here includes a relatively thin sheet such as a film. The thickness of the sheet is usually 0.02 to 1.0 mm, preferably 0.1 to 1.0 mm.

Further, in the above-mentioned laminated foam, a non-woven fabric, a metal foil, a decorative paper, a printing film, etc. are formed on the surface of the laminated foam according to the application requiring a beautiful surface, within the range not impairing the object of the present invention. You may laminate. The present invention also includes a molded product obtained by molding the modified polypropylene resin foam and the laminated foam. The shape of the molded product is not particularly limited, but it is preferably a food container shape such as a cup shape, a dish shape, and a lunch box shape.

Further, the modified polypropylene resin foam of the present invention can be produced by combining extrusion foaming, compression foaming, injection foaming, and the like with block molding, plate molding, mold molding and the like. . Below, the method of manufacturing a foam using extrusion foaming is demonstrated. First, a modified polypropylene resin, which is a base resin, is supplied to a foaming extruder. The foaming extruder can use any device commonly used in the art.

A foaming agent is added to the base resin.
The foaming agent is not particularly limited, and any decomposable foaming agent, gas or volatile foaming agent can be used. In addition,
If the camel-type polypropylene resin is used as a base resin, it has a higher melt viscosity than other base resins at the time of molding, so that foaming having sufficient properties even if a gas or volatile foaming agent is used. The body can be manufactured.

Examples of the decomposable foaming agent include inorganic decomposing foaming agents such as ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, ammonium nitrite, calcium azide, sodium azide and sodium borohydride, azodicarbonamide, azobis. Azo compounds such as sulfolamide, azobisisobutyronitrile and diazoaminobenzene, nitroso compounds such as N, N'-dinitrosopentanemethylenetetramine and N, N'-dimethyl-N, N'-dinitrosoterephthalamide, Examples thereof include benzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide and p, p′-oxybisbenzenesulfonyl semicarbazide, p-toluenesulfonyl semicarbazide, trihydrazinotriazine and barium azodicarboxylate. These foaming agents may be used alone or in combination. Further, the addition ratio of the decomposable foaming agent is preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the base resin. Further, a known foaming auxiliary agent may be added in order to control the decomposition temperature, the amount of generated gas and the decomposition rate.

Examples of the gas blowing agent include carbon dioxide gas, propane, neopentane, methyl ether, dichlorodifluoromethane, butane and the like. The gas here is
It means that it is a gas at room temperature. On the other hand, examples of the volatile foaming agent include ether, petroleum ether, acetone, pentane, hexane, isohexane, heptane, isoheptane, benzene and toluene. The addition ratio of the volatile foaming agent is 0.5 with respect to 100 parts by weight of the base resin.
It is preferably about 20 parts by weight.

Of the above foaming agents, butane is particularly preferable. Further, a cell regulator may be added. Examples of the air bubble controlling agent include inorganic powders such as talc and silica, acidic salts of polyvalent carboxylic acids, reaction mixtures of polyvalent carboxylic acids with sodium carbonate or sodium bicarbonate, and the like. The cell regulator is 0.01 to 1.0 with respect to 100 parts by weight of the base resin.
It is preferable to use parts by weight. Further, an ultraviolet absorber, an antioxidant, a coloring agent, etc. can be added if necessary.

The conditions for extrusion foam molding are as follows: The resin is melted by heating at 180 to 240 ° C. in an extruder, and then the die is most suitable for foaming, that is, 145.
Preference is given to pouring and then extruding while adjusting to ˜175 ° C.

[0027]

The function of the modified polypropylene resin foam of the present invention is
Since it is a foamed product of a mixture of 2 wt% or more of an ethylene-butene random copolymer with respect to a polypropylene resin as a base resin, heat resistance, heat insulation,
It is possible to obtain a modified polypropylene resin foam which has excellent chemical resistance and does not crack during storage under freezing and transportation at low temperatures, and which has excellent impact resistance.

The reason why the ethylene-butene random copolymer used in the present invention does not impair the foamability of the polypropylene resin and improves the impact resistance at low temperature is not clear, but the reason is as follows. Conceivable. In the case of a mixture of polyethylene resin or ethylene-propylene rubber and polypropylene-based resin, since these are substantially incompatible resins, polyethylene resin or ethylene-propylene rubber is present in the amorphous phase of polypropylene-based resin Conceivable. It is considered that the non-crystalline phase portion gives a non-uniform crystal structure during the progress of crystallization, that is, during the growth of the foamed cells, and as a result, the elongation of the wall of the cell is reduced, thereby hindering the foamability.

On the other hand, in the case of a mixture of an ethylene-butene random copolymer and a polypropylene resin, the ethylene-butene random copolymer has a low crystallization temperature, so that crystallization is inhibited during the growth of foam cells. As a result, it is considered that the foamability is less deteriorated than the polyethylene resin or the ethylene-propylene rubber. On the other hand, the impact resistance is affected by the amorphous phase of the polypropylene resin, and therefore the miscibility of the resin contained in the amorphous phase and the polypropylene resin is important. From this perspective,
It is considered that this is because the ethylene-butene random copolymer and the amorphous phase of the polypropylene-based resin have better miscibility than other resins.

[0030]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. Examples 1 to 16 and Comparative Examples 1 to 15 First, the resins used in Examples and Comparative Examples are shown in Table 1 together with their properties.

[0031]

[Table 1]

As shown in Table 2, the resins of Table 1 were combined to produce a foam by the following steps. First, a base resin was mixed with a certain amount of a cell regulator, and this mixture was supplied to a foaming extruder composed of a first extruder and a second extruder having a diameter of φ50 to φ65 mm. For the supplied resin, first
In the central zone of the extruder, inject butane as a blowing agent,
Melt kneaded. Thereafter, the resin was conveyed to a second extruder, poured into a mold having a diameter of 80 mm and kept at the most suitable temperature for foaming, and further extruded from a slit having a die gap of 0.8 mm to obtain a tubular foam. . This tubular foam was taken out along a sizing drum having an outer diameter of 205 mm and cut at one point on the circumference with a cutter to obtain a foam sheet having the density and thickness shown in Table 2.

In Example 15, except that 15% by weight of talc was mixed with the base resin, based on the total weight of the resin.
A foamed sheet manufactured in the same manner as above. Furthermore, in Example 16, 0.2 m is provided on one side of the foamed sheet of Example 5.
m ethylene-propylene block copolymer (resin C)
It is a laminated foam sheet having an overall density of 0.30 g / cm ³ , which is obtained by laminating a resin composed of (1) by a coextrusion method. Comparative Example 9 is a foamed sheet manufactured based on the description of Examples in JP-A-6-212007.

The impact height at low temperature of the obtained foamed sheet was measured by the following method and shown in Table 2 together with the evaluation. -Method of measuring impact height at low temperature In a thermostat of -30 ° C, the pieces (50 mm x 140 mm) of the foamed sheets obtained in Examples and Comparative Examples are horizontally positioned at the bottom of the thermostat. Hold with a clamp (distance between clamps 100 mm). Next, with respect to the held foam sheet, iron balls (diameter 41.3 mm, weight 286 g) were dropped from an arbitrary height so as to drop vertically and almost at the center.
To drop. The height at which the foamed sheet cracked or cracked was defined as the impact height. However, the value of the impact height shown in Table 2 is an average value obtained by measuring 5 times in each of the longitudinal direction and the lateral direction of the foamed sheet. Further, in Table 2, ◯ means that the value of the impact height is 100 mm or more, and x means that the value is less than 100 mm.

[0035]

[Table 2]

As shown in Table 2, the modified polypropylene resin foam of the present invention has better impact resistance at low temperature than the foam sheet of the comparative example, and its surface is beautiful and smooth. Is. Further, in Comparative Examples 11 to 13, phenomena such as poor dispersion of resin, breakage of bubbles, and poor elongation occur,
Could not be foamed sheet. Furthermore, Example 3
6 to 6 and the foamed sheets obtained in Comparative Example 3 were molded into a shape shown in FIGS. 2 to 4 by a known method, the same as in the case of molding a foamed sheet of polypropylene resin alone (Comparative Example 3). , Could be easily molded. In addition,
2 shows a top view (a) and a side view (b) of the cup container, FIG. 3 shows a top view (a) and a side view (b) of the dish-shaped container, and FIG. 4 shows a top view of the lunch box container ( a) and side view (b)
Is shown.

[0037]

EFFECTS OF THE INVENTION The modified polypropylene resin foam of the present invention is a foamed product of a mixture of an ethylene-butene random copolymer in an amount of 2% by weight or more with respect to the base material polypropylene resin. And Therefore, since the main component is a polypropylene resin having excellent heat resistance, it has excellent heat resistance, heat insulation, and chemical resistance, and does not crack during storage at low temperatures and during transportation, and has excellent impact resistance. A modified polypropylene resin foam having a wide operating temperature range can be obtained.

Further, an ethylene-butene random copolymer
Is mixed by 2 to 40% by weight,
To further improve the properties of high quality polypropylene resin foam
You can In addition, polypropylene resin is
The child mass Mz is at least 2.0 × 10 ⁶Mz / Mw
(Weight average molecular weight) of 3.0 or more and high molecular weight region
The overhang of the curve showing that the region contains a branched polymer
A camel-type molecular weight distribution curve (gel permeation
Foaming by
When the melt viscosity increases, it is necessary to use a decomposable foaming agent.
No, use volatile foaming agent similar to styrene resin
A foam can be easily obtained by the foaming.

Further, on at least one side of the modified propylene resin foam, a propylene homopolymer, ethylene-
Propylene copolymer, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene-propylene rubber, ethylene-
A laminated foam formed by laminating sheets made of any one of butene random copolymers or a mixture thereof can be used for applications requiring a beautiful surface.

The molded product molded from the above-mentioned foam can be suitably used for a container used for cooking frozen foods in a microwave oven.

[Brief description of drawings]

FIG. 1 is a graph showing a molecular weight distribution curve of a camel polypropylene resin and other polypropylene resins.

2A and 2B are a top view and a side view of cup containers of Examples and Comparative Examples of the present invention.

FIG. 3 is a top view and a side view of a dish-shaped container of an example of the present invention and a comparative example.

4A and 4B are a top view and a side view of lunch boxes according to examples and comparative examples of the present invention.

Claims (5)

[Claims] 1. A modified polypropylene resin foam, which is a mixture of 2% by weight or more of an ethylene-butene random copolymer mixed with a polypropylene resin as a base resin. 2. An ethylene-butene random copolymer,
The foam according to claim 1, which is mixed in an amount of 2 to 40% by weight. 3. The polypropylene resin has a Z-average molecular weight Mz of at least 2.0 × 10 ⁶ and a Mz / Mw (weight average molecular weight) of 3.0 or more, and contains a branched polymer in the polymer region. The foam according to claim 1, which has a camel-type molecular weight distribution curve (according to gel permeation chromatograph) in which a curve indicating the above is present. 4. A propylene homopolymer, an ethylene-propylene copolymer, a high-density polyethylene, a low-density polyethylene, and a linear low-molecular weight resin on at least one surface of the modified propylene-based resin foam according to claim 1. A laminated foam formed by laminating sheets made of any one of high-density polyethylene, linear ultra-low-density polyethylene, ethylene-propylene rubber, and ethylene-butene random copolymer, or a mixture thereof. 5. A molded product molded from the foam according to claim 1.