JP3281546B2 - Modified polypropylene resin foam, laminated foam and molded articles obtained therefrom - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a modified polypropylene resin foam, a laminated foam, and a molded article obtained therefrom. More specifically, the present invention relates to a modified polypropylene-based resin foam, a laminated foam and a foam obtained therefrom which can be used, for example, for heating in a microwave oven or the like, and which does not crack even when used for storage and transportation at a low temperature. Related to molded articles. Further, the modified polypropylene-based resin foam of the present invention, the laminated foam, and the molded product obtained therefrom can be used for packaging materials, heat insulating materials, and structural materials.

[0002]

2. Description of the Related Art
As a food container that can be used for cooking in a microwave oven, a molded article made of a polypropylene foam is used. Since this molded article is excellent in heat resistance, heat insulation property and chemical resistance, it is excellent as a food container and very useful. However, there is a problem that the glass transition point is generally around 0 ° C., and the glass is broken when used for freezing at −30 ° C.

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

More specifically, the method using a copolymer of propylene and ethylene is superior in the impact resistance at room temperature to the method using a propylene homopolymer. However, the impact resistance at low temperatures of both methods was slightly different. It is known that a foam having improved flexibility can be obtained by a method of mixing a polyethylene resin (JP-A-8-120106).
However, although this method improves flexibility, it has little effect on impact resistance.

[0005] Examples of the rubber-based resin used in the method of mixing various rubber-based resins include, for example, propylene-ethylene rubber, which is often used for improving the impact resistance of a polypropylene-based resin. When this propylene-ethylene rubber is mixed, at least 20 parts of the polypropylene resin are required to impart impact resistance at a low temperature.
It is necessary to add more than weight%.

When this method is used in a non-foaming step, it is common to extrude the foamed resin at a temperature several tens of degrees higher than the melting point of the polypropylene resin. Propylene-ethylene rubber can be mixed in a wide range with the polypropylene resin. However, in the case of having a foaming step, it is necessary to apply a sufficient tension to the resin in order to prevent the bubbles from being broken at the time of bubble growth. Therefore, it is necessary to lower the temperature of the resin to near the melting point. In general, a polypropylene resin having a low fluidity is used, so that a mixed state with other resins is deteriorated. As a result, only high-density foams with a high open cell ratio or foams with poor surface smoothness can be obtained, so that the mixing amount of the rubber-based resin is limited to a very small amount. Could not be granted.

Japanese Patent Application Laid-Open No. 6-212007 discloses a polypropylene block copolymer comprising polypropylene and an ethylene / α-olefin copolymer, and an ethylene / α-olefin copolymer. A polypropylene foam sheet using polyethylene as a base resin is described. This publication aims to obtain a polypropylene foam sheet having excellent impact resistance,
The example describes a foamed sheet using a polypropylene block copolymer containing an ethylene / propylene copolymer, an ethylene / 1-butene copolymer, and optionally polyethylene. However, according to the findings of the inventors of the present invention, it has been found that even the polypropylene-based foam sheet described in this publication has insufficient impact resistance at low temperatures.

In view of the above problems, the inventors of the present invention have:
As a result of diligent examination, it has excellent heat resistance, heat insulation and chemical resistance,
In particular, it does not crack during frozen storage at low temperatures and during transportation,
The present inventors have found a modified polypropylene resin foam having excellent impact resistance, a laminated foam, and molded articles obtained therefrom, and have reached the present invention.

[0009]

Thus, according to the present invention , octe is used for a polypropylene resin as a base resin.
Content is 5 to 30% by weight, and density is 0.86 to
A modified polypropylene resin foam is provided, which is a foam of a mixture obtained by mixing 10 to 30% by weight of an ethylene-octene copolymer of 0.92 g / cm ³ . Furthermore, according to the present invention, the polypropylene
2 weight of ethylene-octene copolymer with respect to ethylene resin
% Of the mixture foamed, and the base resin
The propylene resin has a Z-average molecular weight Mz of 2.0 × 10
Mz / Mw (weight average molecular weight) of ⁶ to 10 × 10 ⁷ .
0 to 20.0, and a branched polymer in a polymer region.
Camel type part with overhang of curve indicating that it contains
Molecular weight distribution curve (gel permeation chromatograph
(Modified polypropylene) characterized by having
A resin-based foam is provided. According to the present invention, at least one surface of the modified propylene-based resin foam,
Propylene homopolymer, ethylene-propylene copolymer, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene-propylene rubber, ethylene-butene random copolymer, ethylene- There is provided a laminated foam formed by laminating sheets made of any one of octene copolymers or a mixture thereof. Further, according to the present invention, there is provided a molded article comprising the modified propylene-based resin foam and the laminated foam.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polypropylene resin which can be used as a base resin in the present invention is not particularly limited, and any known resin can be used. Among known resins, Z-average molecular weight Mz is 2.0 × 10 ⁶ to 10 × 10 ⁷ and Mz /
A Camel-type molecular weight distribution curve (based on gel permeation chromatography) having an Mw (weight average molecular weight) of 3.0 to 20.0 and an overhang of a curve indicating that the polymer region contains a branched polymer is shown. Propylene homopolymer (referred to as camel-type polypropylene-based resin). If Mz is less than 2.0 × 10 ⁶ , viscoelasticity suitable for foaming cannot be obtained, which is not preferable. When Mz exceeds 10 × 10 ⁷ , the load increases. Also, Mz /
When Mw is less than 3.0, the temperature for foaming suitability becomes narrow, and a uniform foam cannot be obtained, which is not preferable. Mz / Mw
Exceeds 20.0, the molecular weight distribution becomes too wide, making it difficult to achieve foaming conditions. Note that Mz is 2.0 × 10
^{The range of 6 to} 5.0 × 10 ⁶ and Mz / Mw of 5 to 10 is particularly preferable. In addition, the propylene homopolymer may have 1 to 1
Ethylene and propylene copolymers containing 0% by weight of ethylene can also be used. In addition, this copolymer includes both a block copolymer and a random copolymer.

In the above resin, the Z average molecular weight Mz is
The average molecular weight at which the distribution on the higher molecular weight side is emphasized by measurement by gel permeation chromatography (hereinafter referred to as GPC), and means the average value of the cube of the molecular weight. The weight-average molecular weight Mw is an average molecular weight obtained when a measured physical property value is directly related to the weight of a polymer, and is 2% of the molecular weight.
Mean power. The method of measuring GPC performed in the present invention is as follows.

Measuring device: GPC 150-C type (manufactured by Water) Measuring conditions: two columns KF-80M (manufactured by SHOdex) Column temperature 145 ° C. (polypropylene resin, hereinafter referred to as PP) Injection temperature 145 ° C. Pump temperature 60 ° C Sensitivity 32 Solvent used o-dichlorobenzene (1.0 ml / min) Scanning time 50 min Injection volume 400 μl If such a polypropylene resin is used, sufficient melting tension can be obtained at the time of foaming, and foaming of a desired density can be obtained. You can get the body.

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

Specific examples of the polypropylene resin that can be used in the present invention include MH-8 manufactured by Mitsubishi Chemical Corporation, and A resin manufactured by Sumitomo Chemical Co., Ltd.
D571, S-131 and the like. In addition, camel-type polypropylene-based resins specifically include X-1005, PF-814, SD-632, and X11 manufactured by Himont.
277-22-1 and the like. In addition, PF-81
4, X-10005 is a propylene homopolymer, and S
D-632 and X11277-22-1 are propylene-ethylene block copolymers.

The base resin is mixed with an ethylene-octene copolymer as a modifier in an amount of 2% by weight or more. The ethylene-octene copolymer that can be used in the present invention has an octene content of 5 to 30% by weight and a density of 0.86 to 0.9.
Those having ² g / cm ² are preferred. In particular, the octene content is 20 to 30% by weight, the density is 0.86 to 0.88 g / cm.
^Two are preferred.

The ethylene-octene copolymer satisfying the above conditions is specifically EG8100 manufactured by Dow Chemical Company.
(Octene content 24% by weight). The modified polypropylene resin foam of the present invention contains a polypropylene resin at 98% by weight or less, preferably 98 to 60% by weight, and an ethylene-octene copolymer at 2% by weight or more, preferably 2 to 40% by weight. ing. Here, when the content of the polypropylene-based resin is more than 98% by weight, the effect of improving the low-temperature impact resistance is small. On the other hand, if the content of the ethylene-octene copolymer is more than 40% by weight, the strength of the foam is reduced, and if it is less than 2% by weight, there is no effect of improving the low temperature impact resistance.

The modified polypropylene resin foam of the present invention includes polyethylene resin, other α-olefin polymers, ionomers, and the like as long as physical properties such as foaming property, heat resistance and impact resistance are not impaired. A small amount of an elastomer such as ethylene-propylene rubber (EP 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 resin amount in order to improve strength and durability and increase the amount. Examples of the inorganic filler that can be used include, but are not particularly limited to, silica, alumina, titanium oxide, talc, clay, and calcium carbonate.

The modified polypropylene resin foam of the present invention preferably has a density of 0.6 to 0.02 g / cm ³ , 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 have the shape of a sheet plate or a tube. When formed into a sheet plate, the 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, Also provided is a laminated foam formed by laminating sheets of any one of linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene-propylene rubber, and ethylene-octene copolymer, or a mixture thereof. . The sheets to be laminated include relatively thin sheets such as films. The thickness of the sheet is usually 0.02-
It is 1.0 mm, preferably 0.1 to 1.0 mm.

Further, the above-mentioned laminated foam may be coated with a nonwoven fabric, a metal foil, a decorative paper, a printed film or the like on the surface thereof in accordance with the use requiring a beautiful surface, as long as the object of the present invention is not hindered. They may be stacked. 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 is preferably a food container shape such as a cup shape, a dish shape, and a lunch container 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 methods such as block molding, plate molding and molding. . Hereinafter, a method for producing a foam using extrusion foam molding will be described. First, a modified polypropylene resin as a base resin is supplied to a foam extruder. As the foaming extruder, any device generally used in the art can be used.

A foaming agent is added to the base resin.
The foaming agent is not particularly limited, and any of a decomposable foaming agent, a gaseous or volatile foaming agent can be used. In addition,
If the above-mentioned camel-type polypropylene-based resin is used as the base resin, since the melt viscosity is higher than the other base resins during molding, foaming having sufficient properties even when a gas or volatile blowing agent is used. The body can be manufactured.

Examples of the decomposable blowing agent include inorganic decomposable blowing agents such as ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, ammonium nitrite, calcium azide, sodium azide, sodium borohydride, azodicarbonamide, azobis Azo compounds such as sulfformamide, azobisisobutyronitrile and diazoaminobenzene, nitroso compounds such as N, N'-dinitrosopentamethylenetetramine and N, N'-dimethyl-N, N'-dinitrosoterephthalamide; Examples include benzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide and p, p'-oxybisbenzenesulfonyl semicarbazide, p-toluenesulfonyl semicarbazide, trihydrazinotriazine, barium azodicarboxylate and the like. These blowing 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 based on 100 parts by weight of the base resin. Further, in order to adjust the decomposition temperature, the amount of generated gas, and the decomposition rate, a known foaming aid can be added.

Examples of gaseous blowing agents include carbon dioxide, propane, neopentane, methyl ether, methane difluoride methane, and butane. In addition, the gas here means
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 gas and the volatile foaming agent is preferably 0.5 to 20 parts by weight based on 100 parts by weight of the base resin.

Of the above foaming agents, butane is particularly preferred. Further, a bubble regulator may be added. Examples of the foam control agent include inorganic powders such as talc and silica, acidic salts of polycarboxylic acids, and reaction mixtures of polycarboxylic acids with sodium carbonate or sodium bicarbonate. The foam controlling agent is used in an amount of 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, if necessary, an ultraviolet absorber, an antioxidant, a coloring agent, and the like can be added.

Here, the conditions for the extrusion foaming molding are such that the resin is melted by heating to 180 to 240 ° C. in an extruder, and then the temperature most suitable for foaming, ie, 145, is applied to a die.
It is preferred to inject while adjusting to １７175 ° C. and then extrude.

The modified polypropylene resin foam of the present invention is characterized in that it is a foam of a mixture in which 2% by weight or more of an ethylene-octene copolymer is mixed with a polypropylene resin as a base resin. It is possible to obtain a modified polypropylene resin foam having excellent impact resistance, which is excellent in heat resistance, heat insulating properties and chemical resistance and which does not crack particularly during frozen storage at low temperatures and during transportation.

The ethylene-octene copolymer used in the present invention does not inhibit the foamability of the polypropylene resin,
Although the cause of improving the impact resistance at low temperatures is not clear,
It is considered as follows. In the case of a mixture of a polyethylene resin or an ethylene-propylene rubber and a polypropylene resin, since these are substantially incompatible resins, the polyethylene resin or the ethylene-propylene rubber may be present in the amorphous phase of the polypropylene resin. Conceivable. It is considered that the non-crystalline phase portion gives a non-uniform crystal structure during the progress of crystallization, that is, at the time of the growth of the foamed cells, and as a result, the expansion of the walls of the cell cells is reduced, thereby inhibiting the foaming property.

On the other hand, in the case of a mixture of an ethylene-octene copolymer and a polypropylene resin, the ethylene-octene copolymer has a low crystallization temperature, so that crystallization is not hindered during the growth of foamed cells. As a result, it is considered that the foamability is less reduced than the above-mentioned polyethylene resin or ethylene-propylene rubber. On the other hand, since the amorphous phase of the polypropylene-based resin has an important influence on the impact resistance, the miscibility of the resin contained in the amorphous phase with the polypropylene-based resin is important. From this viewpoint, it is considered that the ethylene-octene copolymer and the amorphous phase of the polypropylene-based resin have better miscibility than other resins.

[0030]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Examples 1 to 11 and Comparative Examples 1 to 10 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, by combining the resins of Table 1, a foam was produced in 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 comprising a first extruder and a second extruder having a diameter of 50 to 65 mm. In the supplied resin, the first
In the central zone of the extruder, butane is injected as blowing agent,
It was melt-kneaded. Thereafter, the resin was conveyed to the second extruder, poured into a mold having a diameter of φ80 mm maintained at a temperature most suitable 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 shape of 205 mm and cut at one point on the circumference by a cutter to obtain a foam sheet having the density and thickness shown in Table 2.

The low-temperature impact height of the obtained foamed sheet was measured by the following method, and the evaluation results are shown in Table 2. Method for measuring impact height at low temperature A section (50 mm x 140 mm) of the foam sheet obtained in each of the examples and comparative examples is placed horizontally at the bottom of the constant temperature bath in a constant temperature bath at -30 ° C. Hold with clamps (distance between clamps 100 mm). Next, an iron ball (diameter: 41.3 mm, weight: 286 g) is dropped from the arbitrary height so as to drop vertically and almost to the center with respect to the held foam sheet.
Drop. The height at which cracks or cracks occurred in the foamed sheet was defined as the impact height. However, the values of the impact height shown in Table 2 are measured five times in each of the longitudinal direction and the lateral direction of the foam sheet, and the average value is shown. Further, in Table 2, ○ means the case where the value of the impact height is 100 mm or more, and × means the case where the value is less than 100 mm.

[0034]

[Table 2]

As shown in Table 2, the modified polypropylene resin foam of the present invention has good low-temperature impact resistance and a beautiful and smooth surface compared to the foam sheet of the comparative example. It is. Further, in Comparative Examples 6 to 8, phenomena such as poor resin dispersion, breakage of air bubbles, and poor elongation occurred, and it was not possible to obtain a foamed sheet. Further, Examples 3 to 6
When the foamed sheet obtained in was molded into a shape shown in FIGS. 2 to 4 by a known method, it could be easily molded. 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-like container, and FIG. 4 shows a top view of the lunch container. The figure (a) and the side view (b) are shown.

[0036]

The modified polypropylene resin foam of the present invention is characterized in that it is a foam of a mixture obtained by mixing at least 2% by weight of an ethylene-octene copolymer with a polypropylene resin as a base resin. I do. Therefore, since the main component is a polypropylene resin having excellent heat resistance, heat resistance,
It is possible to obtain a modified polypropylene-based resin foam having excellent heat resistance and excellent impact resistance, which is excellent in heat insulation and chemical resistance.

Further, the ethylene-octene copolymer has 2
By mixing up to 40% by weight, the properties of the modified polypropylene resin foam can be further improved. Further, the polypropylene resin has a Z average molecular weight M
z is 2.0 × 10 ⁶ to 10 × 10 ⁷ , Mz / Mw (weight average molecular weight) is 3.0 to 20.0, and there is an overhang of a curve indicating that the polymer region contains a branched polymer. Having a camel-type molecular weight distribution curve (based on gel permeation chromatography) increases the melt viscosity during foaming and eliminates the need to use a decomposable foaming agent. A foam can be easily obtained by foaming using the agent.

Further, 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-
Butene random copolymer, ethylene-octene copolymer either alone or a laminated foam formed by laminating sheets composed of a mixture thereof, can also be used in applications where surface beauty is required. .

Further, the molded article formed from the above-mentioned foam can be suitably used especially for a container used for cooking frozen food in a microwave oven.

[Brief description of the drawings]

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

FIG. 2 is a top view and a side view of a cup container according to an example of the present invention and a comparative example.

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

FIG. 4 is a top view and a side view of a lunch container of an example and a comparative example of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C08J 9/04 B32B 5 / 18,27 / 32

Claims (4)

(57) [Claims] An octene content of 5 to 30% by weight based on a polypropylene resin as a base resin and a density of
A modified polypropylene-based resin foam, which is a foam obtained by mixing 10 to 30% by weight of an ethylene-octene copolymer having a weight ratio of 0.86 to 0.92 g / cm ³ . 2. The method according to claim 1, wherein the base resin is a polypropylene resin.
2% by weight or more of ethylene-octene copolymer
It is a foam of a mixture, and the polypropylene resin as a base resin has a Z average molecular weight Mz of 2.0 × 10 ⁶ to 10 × 10 ⁷
And Mz / Mw (weight average molecular weight) is 3.0 to 20.0, and a camel-type molecular weight distribution curve (gel permeation chromatograph) having an overhang of a curve indicating that a branched polymer is contained in a high molecular region. (1) a modified polypropylene resin foam , characterized in that: 3. The modified propylene-based resin foam according to claim 1 or 2 , wherein at least one surface of the foam comprises a propylene homopolymer, an ethylene-propylene copolymer, a high-density polyethylene, a low-density polyethylene, a linear low-density polyethylene, A laminated foam formed by laminating sheets made of any one of linear ultra-low density polyethylene, ethylene-propylene rubber, ethylene-butene random copolymer, and ethylene-octene copolymer, or a mixture thereof. 4. The method of claim 1 to 3 of any one of a molded article formed by molding a foam.