JP2000273232A - Heat-insulating foamed material composed of polypropylene resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foamed material composed of a polypropylene resin composition containing a polypropylene resin as a main component and having low density, high closed cell ratio and excellent heat-insulation performance. SOLUTION: The heat-insulating foamed material composed mainly of a polypropylene resin has high heat-insulation performance by controlling the density, closed cell ratio and foam diameter without depending upon the gas generated from a foaming agent. Concretely, the heat-insulating polypropylene resin material contains >=50 wt.% polypropylene resin and has a density of 50-10 kg/m3, a closed cell ratio of >=50%, an average foam diameter of <=1.5 mm and a thermal conductivity of <=0.040 W/m.K (0.034 kcal/m.h. deg.C) at an average temperature of 20 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat insulating foam made of a polypropylene resin. More specifically, the present invention relates to a foam made of a polypropylene resin having a thermal conductivity of 0.040 W / m · K or less, which can be suitably used for a structural material such as a building wall, a floor partition, a heat insulating material, and the like.

[0002]

2. Description of the Related Art In general, a foam made of a thermoplastic resin is lightweight and has good heat insulating properties and good buffering properties against external stress. Therefore, it is widely used as a heat insulating material, a cushioning material, a core material, a food container and the like. It's being used. Above all, foams made of a polypropylene-based resin have good chemical resistance, impact resistance, and heat resistance, and are therefore particularly preferably used as cushioning materials. However, when a foam made of a polypropylene resin is used as a heat insulating material, the polypropylene resin has a low gas barrier property, so that a gas having a low thermal conductivity generated from a foaming agent is easily dissipated to the outside from bubbles, and a foam having excellent heat insulation performance. It is very difficult to get.

[0003] Further, since the polypropylene resin is a crystalline resin, the viscosity and tensile strength at the time of melting are low, and when the resin is foamed, the strength of the cell wall is not sufficiently maintained at the time of foaming. In addition, as the cross-sectional area of the foam at the time of post-molding increases, the cell diameter increases, the cell wall breaks, and a foam having a high closed cell rate cannot be obtained. Therefore, it is difficult to obtain a low-density foam having a uniform internal cell state, a high closed cell ratio and a small cell diameter by foaming the polypropylene resin.

It is conventionally known that it is difficult to obtain a foam made of a polypropylene resin having a high closed cell ratio and excellent heat insulation performance.

[0005] In an attempt to overcome such difficulties,
In recent years, Japanese Patent Publication No. Hei 8-504471 discloses a foaming factor F
(Foam density × average cell diameter × tan δ ^0.75 ) <1.8
Are disclosed. Further, JP-A-7
JP-A-252318 discloses a thick polypropylene foam having a specified biaxial elongational viscosity.

However, even with these methods, it is still difficult to obtain a sufficient foam.

[0007] At present, there has not been found any method for producing a foam by extrusion foaming in which the foaming property of the polypropylene resin is improved and the closed cell ratio is high and the heat insulating property is excellent.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a foam made of a polypropylene-based resin containing a polypropylene-based resin as a main component, which has a low density, a high closed-cell ratio, and excellent heat insulating properties.

[0009]

The heat-insulating foam of the present invention containing a polypropylene-based resin as a main component can control the density, closed cell rate, and cell diameter without depending on the gas generated from the foaming agent. , To achieve high heat insulation.

The present invention has a density of 50 to 10 kg / m ³ , a closed cell ratio of 50% or more, an average cell diameter of 1.5 mm or less, and a thermal conductivity of 0.040 W / m at an average temperature of 20 ° C.
m · K (0.034 kcal / m · h · ° C.) or less, characterized by being 50% by weight of a polypropylene resin.
The present invention relates to a foam comprising the above-mentioned polypropylene-based resin.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of various studies, we have found that by controlling the density, closed cell ratio, and cell diameter of a foam to specific ranges, the thermal conductivity of the obtained foam is 0.040 W / m.
・ We have found that it can be achieved below K. Heretofore, a foam comprising a polypropylene-based resin composition containing a polypropylene-based resin having a high closed-cell rate and excellent heat-insulating properties as a main component has not been known at all, and is surprising.

In the present invention, the density of the foam is 50 to 10
kg / m ³ . More preferably, 30 to 15 kg / m ³
It is.

The closed cell ratio is 50% or more. It is more preferably at least 80%. The average bubble diameter is 1.5 mm or less. More preferably, it is 1.0 mm or less. The thickness is preferably at least 10 mm, more preferably at least 20 mm. The polypropylene resin is not particularly limited, but preferably a polypropylene resin having a melt tension at 230 ° C. of 5 g or more should be used.

Examples of the polypropylene resin having a melt tension at 230 ° C. of 5 g or more include irradiating a linear polypropylene resin with radiation or melting and mixing a linear polypropylene resin, a radical polymerization initiator, and a monomer. And a polypropylene resin containing a branched structure or a high molecular weight component obtained by the above method. Among them, a modified polypropylene resin obtained by melt-mixing a linear polypropylene resin, a radical polymerization initiator and a monomer at a temperature not lower than the temperature at which the radical polymerization initiator is decomposed can be produced at a low cost.

As the monomers, styrene monomers, isoprene monomers and 1,3-butadiene monomers may be used alone or in combination.

The melt kneading apparatus includes a roll,
Kneaders such as co-kneaders, Banbury mixers, Brabenders, single-screw extruders, twin-screw extruders, twin-screw surface renewers,
Examples of such devices include a horizontal stirrer such as a multi-shaft disk device or a vertical stirrer such as a double helical ribbon stirrer, which can heat a polymer material to an appropriate temperature and knead it while applying an appropriate shear stress. Of these, especially uniaxial or 2
A screw extruder is preferred in terms of productivity.

As described above, the modified polypropylene resin of the present invention can be produced.

If necessary, the modified polypropylene resin may be a polyolefin resin such as high-density polyethylene or low-density polyethylene, a polystyrene resin such as polystyrene or styrene-acrylonitrile copolymer, an ethylene propylene rubber, an ethylene propylene diene rubber or the like. A styrene-based elastomer such as an olefin-based elastomer, styrene-butadiene rubber, styrene-butadiene-styrene rubber, styrene-ethylene-propylene-propylene rubber or a modified polypropylene-based resin having at least two kinds of at least 5
You may add in the range which becomes 0 weight% or more.

As a specific method for producing the foam of the present invention, for example, a modified polypropylene-based resin, a modified polypropylene-based resin composition comprising a foaming agent and other optional materials to be added are extruded. After melt kneading in a machine and adjusting the temperature of the mixture to a temperature suitable for foaming, a method of obtaining an extruded foam by post-molding, a modified polypropylene resin in a molten state, and if necessary, added. And a method in which a foaming agent is added or press-fitted to the other additive materials, the modified polypropylene resin composition is adjusted to a temperature suitable for foaming, and then an extruded foam is formed by post-molding. Here, the post-forming is a forming step using a forming die and a sizing die, and the shape of the forming die and the sizing die is not particularly limited. However, the ratio of the cross-sectional area of the foam after post-forming to the foam before free-forming (free foam) (S2 (cross-sectional area of foam after post-forming) / S1 (cross-sectional area of free foam)) It is indispensable to achieve the present invention to set the molding conditions to 3 to 1 times. That is, when S2 / S1 is more than three times, it is generally difficult to maintain foaming characteristics such as a closed cell ratio and a bubble diameter in free foaming. Furthermore, the ratio (THD / TMD) of the cell diameter in the thickness direction (THD) to the cell diameter in the extrusion direction (TMD) of the obtained foam is 0.5 to
It is desirable to select molding conditions that result in 2.

The extruder is not particularly limited as long as it can heat the modified polypropylene resin in a molten state and can knead it while giving an appropriate shear stress. The extruder may be a single-screw or twin-screw extruder. . Further, these extruders may be used in combination with two, three or multiple stages in series. In particular, make the mixture composition of the modified polypropylene resin and the foaming agent uniform,
From the viewpoint of productivity, a two-stage tandem extruder is more preferable.

As the foaming agent, for example, propane,
Aliphatic hydrocarbons such as butane, pentane, hexane and heptane; alicyclic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane; inorganic gases such as carbon dioxide, nitrogen and air; one or two kinds of water and the like The above is mentioned.

The addition amount (kneading amount) of the blowing agent varies depending on the type of the blowing agent and the target expansion ratio, but is preferably in the range of 2 to 50 parts by weight based on 100 parts by weight of the polypropylene resin.

In order to control the cell diameter of the foam to an appropriate size, if necessary, sodium bicarbonate may be used.
A foam nucleating agent such as citric acid or talc or mica may be used in combination. Usually, the addition amount of the foam nucleating agent used as needed is preferably 0.01 to 5 parts by weight based on 100 parts by weight of the polypropylene resin.

The foam of the present invention is a low-density foam having a uniform internal cell state, a lightweight, beautiful appearance, a high closed cell ratio and excellent heat insulating properties, and is extremely useful as a heat insulating material. is there.

[0025]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to only these examples.

The evaluation methods used in the examples and comparative examples are summarized below. (Melt tension) Using a melt tension tester manufactured by Toyo Seiki, a polypropylene resin heated to 230 ° C from an orifice having a diameter of 1 mm, a length of 10 mm, and an inflow angle of 45 ° is extruded from a capillary at a rate of 10 mm / min, and the extruded product is extruded. Winding while passing through a tension detection pulley 35 cm away from the capillary outlet and accelerating from a speed of 1 m / min at an acceleration of 40 m / min ² ,
The tension required to take up the extrudate until it is cut is measured. (Measurement of Thermal Conductivity) A molded body of 200 × 200 × 15 mm was cut out and measured by a flat plate direct method according to JIS A1412. Using a thermal conductivity measuring device (manufactured by Eiko Seiki: HC-072), the measurement conditions were as follows: a hot plate 3 under a load of 250 kg / m ^2.
The thermal conductivity was measured at an average temperature of about 20 ° C. when the temperature and heat flow were stabilized while maintaining the temperature at 6.6 ° C. and the low heat plate at 6.6 ° C. (Independent cell ratio) Measured by an air pycnometer according to the method described in ASTM D-2856 (Average cell diameter) Cell diameter in the thickness direction (THD): Thickness direction of foam (H
D) The value obtained by measuring the bubble chord length on the straight line and multiplying by 1.626.

Cell diameter in extrusion direction (TMD): The cell chord length on a straight line in the extrusion direction (MD) of the foam was measured, and 1.62.
Value multiplied by 6.

Average cell diameter: thickness direction (H
D) The bubble chord length on a straight line in the width direction (TD) and the extrusion direction (MD) was measured, multiplied by 1.626, and the average value in three directions.

Cell diameter = 1.626 × cell chord length on a straight line (cross-sectional area of foam) A cross section of the foam is sliced to a thickness of about 1 mm, and this foam is projected on paper. Next, the paper is cut out along the projected foam shape and its weight is measured. The cross-sectional area of the foam was determined from the weight of the obtained paper and the specific gravity of the paper.

(Examples 1 to 12, Comparative Examples 1 to 4) 100 parts by weight of ethylene random polypropylene (Hypol B230 manufactured by Grand Polymer Co., Ltd., MFR 0.5 g, ethylene content 3 wt%), and 1 as a radical polymerization initiator 0.5 parts by weight of 1,1-di (t-butylperoxy) -3,3,5-trimethylcyclohexane (manufactured by NOF CORPORATION, perhexa 3M, 1 minute half-life temperature 147 ° C.), stabilizer (Ciba Geigy) Irganox B225) 0.
A mixture consisting of 2 parts by weight and 0.05 part by weight of a blended oil (Super Ease manufactured by Koshigaya Chemical Co., Ltd.) was stirred and mixed with a super floater. The mixture was put into a hopper opening of a 44 mm twin-screw extruder at 50 kg / hr using a measuring feeder, and an attached liquid feed pump (manufactured by Nikkiso Co., Ltd.) was supplied at a rate of 1.25 kg / hr of isoprene. Diaphragm: About 2.5 parts by weight of isoprene was injected from the middle of the extruder cylinder using a model C22X-08F-14D1D, discharge pressure of 50 kgf / cm2). The mixture was extruded at a rotation speed of 150 rpm at 180 ° C. before injecting isoprene and at 200 ° C. after injecting to produce a modified polypropylene resin having a melt tension of 8 g at 230 ° C.

65 parts by weight of the obtained modified polypropylene resin, 35 parts by weight of a polystyrene resin (Stylon G9305, MFR1.5, manufactured by Asahi Kasei Corporation), a styrene-ethylene-propylene block copolymer (Kuraray Co., Ltd.) Mica powder (YAMAGUCHI MICA POWD) in 5 parts by weight of Septon 2104, MFR 0.4
0.2 parts by weight of mica A21S manufactured by ER Co., Ltd., and 0.1 blend oil (Super Ease manufactured by Koshigaya Chemical Co., Ltd.)
The parts by weight were added and mixed with a ribbon blender. Then, the mixture was supplied to a 65-90 mmφ tandem extruder, and the rotation speed of the first stage extruder (65 mmφ) was set to 80 rpm and the temperature was set to 200
After setting the temperature to 0 ° C and melting the mixture, 15 parts by weight of isobutane as a foaming agent was injected and mixed with 100 parts by weight of the total of the modified polypropylene resin and the polystyrene resin. Next, the mixture is fed to a second-stage extruder (90 mmφ) set at a rotation speed of 8 rpm and a temperature of 138 ° C. In addition, the rotation speed is 7 rpm, the length is 1.5 m, and the temperature is adjusted to 137 ° C.
It is fed to a cooling machine with an inner diameter of 155 mm
The mixture was discharged for 50 minutes at a discharge rate of 50 kg / hr, and the mixture was discharged from a slit die having a width of 50 mm, a die gap of 2.5 mm and a land length of 23 mm to obtain a free foam. Next, this free foam is restrained only in the vertical direction of the foam by using a forming die having a width of 250 mm and a length of 73 mm and a sizing die having a width of 320 mm and a length of 150 mm while maintaining a gap of 20 mm (forming gap) up and down. An extruded foam with a beautiful appearance was obtained by molding. The cross-sectional area of the obtained free foam was 35 cm ² , the foam after molding passed through a forming die and a sizing die was 46 cm ² , and the cross-sectional area was 1.3 times larger than that of the free foam. . The resulting foam has a density of 17 kg /
m ³ , closed cell ratio 80%, average cell diameter 0.9 mm (TH
D / TMD = 1.2) The foam had a beautiful appearance and a thermal conductivity of 0.036 W / m · K.

Table 1 shows that when the molding gap was changed,
Table 2 shows the foaming properties and the heat insulating properties when the amount of the nucleating agent and the molding gap were changed, and Table 3 shows the properties when the amount of the blowing agent was changed.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3] (Examples 13 to 16, Comparative Example 5) The same as Example 1 except that only the modified polypropylene resin was used. Table 4 shows the foaming properties and the heat insulating properties when the molding gap was changed.

[0036]

[Table 4] From the above, the thermal conductivity of a foam made of a polypropylene-based resin containing a polypropylene-based resin as a main component is 0.040.
It can be seen that the W / m · K or less is achieved only when the foam is obtained under very specific conditions and the density, closed cell ratio and cell diameter satisfy specific ranges.

[0037]

The density is 50 to 10 kg / m ³ , the closed cell ratio is 50% or more, the average cell diameter is 1.5 mm or less, and the thermal conductivity at an average temperature of 20 ° C. is 0.040 W / m · K.
(0.034 kcal / m · h · ° C.) or less, and relates to a foam comprising a polypropylene-based resin containing 50% by weight or more of a polypropylene-based resin.
The foam is a low-density foam having a high closed cell ratio and excellent heat insulating properties, and is extremely useful as a heat insulating material.

Continued on front page F-term (reference) 4F074 AA24D BA32 BA33 BA34 BA35 BA36 BA37 BA39 BA40 CA22 CA48 DA02 DA03 DA07 DA12 DA32 4J011 AA05 AB02 PA64 PC08 PC13 PC15 4J026 AA13 BA05 BA46 BA47 DB05 DB13 GA10

Claims (5)

[Claims] 1. A density of 50 to 10 kg / m ³ , a closed cell ratio of 50% or more, an average cell diameter of 1.5 mm or less, and a thermal conductivity at an average temperature of 20 ° C. of 0.040 W / m · K.
(0.034 kcal / m · h · ° C.) or less, a foam comprising a polypropylene-based resin containing 50% by weight or more of a polypropylene-based resin. 2. The ratio of the cross-sectional area of the foam after post-forming to the foam before post-forming (S2 (cross-sectional area of foam after post-forming / S1 (cross-sectional area of foam before post-forming)) The foamed body comprising the polypropylene resin according to claim 1, wherein the molding conditions are set to 3 to 1 times. 3. The foam according to claim 1, wherein the polypropylene resin has a melt tension at 230 ° C. of 5 g or more. 4. The radical polymerization initiator, wherein the polypropylene-based resin decomposes a linear polypropylene-based resin, at least one monomer selected from styrene, isoprene, and 1,3-butadiene, and a radical polymerization initiator. A foam comprising the polypropylene resin composition according to claim 1, which is a modified polypropylene resin obtained by melt-kneading at a temperature or higher. 5. The polypropylene resin composition according to claim 1, wherein the ratio (THD / TMD) of the cell diameter (THD) in the thickness direction of the foam to the cell diameter (TMD) in the extrusion direction is 0.5 to 2. Foam consisting of