JPH0867758A - Polypropylene resin foam and its production - Google Patents

Abstract

PURPOSE: To obtain a PP resin foam by melt-blending a PP resin having a specified melt tension and a specified difference between the melting temperature and the crystallization temperature with a blowing agent and a foaming nucleator in a extruder, extruding the melt, and rapidly cooling the extrudate to form a product having a specified density and a specified thickness. CONSTITUTION: A PP resin in an amount of 100 pts.wt. having a melt tension of 3g or above and a ΔT of 40 deg.C or below [wherein ΔT=Tm -Tcc (wherein Tcc is the crystallization peak temperature as measured when the resin is melted by heating in a nitrogen atmosphere to 200 deg.C at a temperature rise rate of 10 deg.C/min, and the melt is cooled to room temperature at a temperature fall rate of 10 deg.C/min; and Tm is the melting peak temperature as measured when the cooled resin is heated again to 200 deg.C at a temperature rise rate of 10 deg.C/min)] is melt-blended with 10-25 pts.wt. blowing agent (e.g. methyl chloride) and 0.01-1.0 pt.wt. foaming nucleator (e.g. sodium, bicarbonate or citric acid) in an extruder. The melt is extruded at a temperature lower than the Tm by 5-25 deg.C, and the plastic extrudate in a state of cell growth is rapidly cooled and crystallized to obtain the objective PP resin foam in the form a plate having a density of 0.02-0.05g/cm<3> and a thickness of 10mm or above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength, thick-plate-shaped polypropylene resin foam excellent in heat resistance, heat insulation, and mechanical properties such as rigidity and impact resistance, and a method for producing the same. .

[0002]

2. Description of the Related Art As one of the methods for producing a thermoplastic resin foam, a thermoplastic resin is melted in an extruder, and a blowing agent is kneaded to maintain a high pressure, and then the resin is removed from the extruder under a low pressure. The extrusion foaming method of extruding and foaming has been widely used.

Amorphous resins such as polystyrene have been widely used as the resin used in the extrusion foaming method. Amorphous resins are often used because, when heated to a melting temperature or higher, generally, the decrease in melt viscosity with temperature rise is gentle, and therefore, the foaming suitable viscosity range is wide,
This is because extrusion foam molding can be performed relatively easily.

However, in recent years, as the quality of foams has been improved, and in particular, the demands for heat resistance and impact resistance have been improved, olefin resin foams which are foams capable of meeting these demands have been demanded. Is becoming.

Among the above-mentioned olefin resins, polypropylene is a resin which has good heat resistance and impact resistance and can meet the above requirements, but it has a relatively high degree of crystallinity, and its viscoelasticity greatly changes with a slight temperature change. However, there is a problem that the foaming suitable temperature range is extremely narrow and it is difficult to obtain a foam. Therefore, efforts have been made to expand the temperature range suitable for foaming by various methods.

Examples of such methods include crosslinking polypropylene and mixing polypropylene with an amorphous resin such as polystyrene to expand the temperature range suitable for foaming. Further, according to Japanese Patent Laid-Open No. 62-121704, there is proposed a method of expanding the temperature range suitable for foaming by using polypropylene having free-end long chain branching and strain hardening elongation viscosity. , Such resins are actually commercially available.

[0007]

However, there are many problems that the cross-linking of polypropylene causes an increase in cost and deterioration of recyclability.

Further, the one using a mixture of polypropylene and an amorphous resin such as polystyrene does not maintain the original thermal and mechanical properties of polypropylene, and therefore the properties of the foamed product are deteriorated. Have.

Further, according to JP-A-5-506875, when polypropylene having a molecular weight distributed so as to have two peaks (polypropylene corresponding to the polypropylene described in JP-A-62-121704) is used, Space, thickness 0.5 to 5 mm, density 0.05 to 0.5
The sheet-like foam of g / cm ³ can be produced by molding the extruded foamed resin by external cooling (cooling with an air ring, mandrel, etc.) and controlling the cell formation, but the thickness is 10 mm. As described above, the fact is that a thick-plate foam having a density of 0.02 to 0.05 g / cm ^{3 and} a high expansion ratio has not yet been manufactured.

The present invention has been made to solve the problems of the prior art as described above.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, has a melt tension (melt tension) of 3 g or more, and formula (1): ΔT = Tm-Tcc. (1) (In the formula, Tcc is a temperature increase rate of 10 ° C. measured by a differential scanning calorimetry analyzer in a polypropylene atmosphere in a nitrogen atmosphere.
After heating and melting up to 200 ° C at 10 / min, 10 ° C
The crystallization peak temperature, Tm, detected in the process of cooling to room temperature at 10 psi / min, is the melting peak temperature detected in the process of heating the cooled resin again to 200 ° C. at a heating rate of 10 ° C./min. ), A density of 0.02 to 0.
The melt tension is 3 g when extrusion-foaming a polypropylene resin foam and a polypropylene resin foam having a thickness of 05 g / cm ³ and a thickness of 10 mm or more.
It is above, and it is Formula (1): (DELTA) T = Tm-Tcc (1) (In Formula, Tcc is a polypropylene resin in a nitrogen atmosphere, and a temperature rising rate is 10 degreeC / m with a differential scanning calorimetry analyzer.
After heating and melting up to 200 ° C in in, 10 ° C / m
The crystallization peak temperature, Tm, detected in the process of cooling to room temperature with in is the rate of temperature increase of 10 for the cooled resin again.
100 parts by weight of polypropylene-based resin having a ΔT of 40 ° C. or lower at the melting peak temperature detected in the process of heating to 200 ° C. at a heating rate of 200 ° C./min (the same applies hereinafter)
10 to 25 parts of foaming agent and 0.01 to 1.0 of foam nucleating agent
The temperature of the molten mixture held at high pressure in the extruder consisting of 3 parts is kept at 5 to 25 ° C. lower than Tm in formula (1), then extruded out of the extruder, and inside the extruded mixture. The extrudate in the plastic state in the process of bubble growth is rapidly cooled and crystallized, and the density is 0.02-0.05 g / c.
The present invention relates to a method for producing a slab-like polypropylene resin foam having a thickness of m ³ and a thickness of 10 mm or more.

[0012]

EXAMPLES In the present invention, the melt tension is 3 g or more, and the formula (1): ΔT = Tm-Tcc (1) (In the formula, Tcc is a polypropylene resin in a nitrogen atmosphere. Medium, differential scanning calorimetry analyzer temperature rising rate 10 ℃
After heating and melting up to 200 ° C at 10 / min, 10 ° C
The crystallization peak temperature, Tm, detected in the process of cooling to room temperature at 10 psi / min, is the melting peak temperature detected in the process of heating the cooled resin again to 200 ° C. at a heating rate of 10 ° C./min. ), A polypropylene resin having a ΔT of 40 ° C. or less is used.

The polypropylene resin has a melt tension of 3 g or more as described above, but a melt tension of 3 g or more is necessary for producing uniform cells. If this value is less than 3 g, non-uniform cells are generated or foam is broken, and a good foam cannot be manufactured. Melt tension is 1
It is preferably 0 g or more from the viewpoint of maintaining the cell film during bubble generation, and preferably 30 g or less from the viewpoint of securing a foaming ratio with the growth of bubbles.

The melt tension is a polypropylene extruded type plastometer in which a molten polypropylene resin is heated to 180 ° C. and melted by using a Capillograph manufactured by Toyo Seiki Seisakusho Co., Ltd., which is widely used in this area. (Diameter 1 mm, length 10 mm) While pushing down the piston at a constant speed of 1 cm / min, it is extruded in a string shape, and then the string-shaped extrudate is placed under the nozzle 3
After passing through the tension detection pulley located at 5 cm,
It is the tension measured by the tension detection pulley while being wound by a winding roll at a speed of 0.3 m / min.

The polypropylene resin has a ΔT of 4 in ΔT = Tm-Tcc (1) (wherein Tm and Tcc are the same as described above) as described above.
It is a polypropylene resin whose temperature is 0 ° C or lower. The exothermic peak temperature generated during crystal formation detected in the process of heating and melting a polypropylene resin to 200 ° C. by a differential scanning calorimeter and then cooling to room temperature was defined as a crystallization peak temperature Tcc, and was cooled. The endothermic peak temperature at the time of melting detected during the process of heating the resin again is defined as the melting peak temperature Tm, and the temperature difference ΔT = Tm−T between them.
cc is an index of the ease of transition from the molten state to the crystallized state.

The reason for measuring Tm after heating and melting the resin once is to eliminate the influence of factors during resin preparation on Tm.

The temperature difference ΔT is 40 ° C. or less, preferably 10 ° C. or more and 35 ° C. or less. When extruded from the extruder, the polypropylene resin in the process of foaming is efficiently solidified and crystallized by cooling by the heat of vaporization of the foaming agent or forced cooling from the outside of the foam, in order to hold the cell walls, This is because it is preferable that the time from the molten state to the crystallized state is short.

When the temperature difference ΔT exceeds 40 ° C., the polypropylene resin is not solidified or crystallized in a short time after being extruded from the extruder, and therefore the cell wall is hard to be held and the cell breaks. It becomes easy and it becomes difficult to form a good foam.

For the Tm and Tcc, a DSC200 manufactured by Seiko Denshi Kogyo Co., Ltd. was used, and the temperature rising and falling speed was 10
It is measured at ° C / min.

In the present invention, the polypropylene resin is foamed by the extrusion foaming method to have a thickness of 10 at a specific density.
The purpose is to obtain a thick polypropylene resin foam with a thickness of mm or more at low cost and with good recyclability. However, the polypropylene resin after passing through the extruder, that is, the polypropylene resin after foaming is the resin in the extruder. In some cases, the properties may change (for example, when shearing force is applied to the molten resin, which may cause deterioration due to the breaking of molecular chains). The ΔT temperature of the resin shows almost no change as compared with the value of the polypropylene resin before being charged into the extruder.

For the same reason, the melt tension of the polypropylene-based resin after foaming may be lower than the melt tension of the polypropylene-based resin before being charged into the extruder, but the decrease is due to the melt tension in the present invention. It is not in the range that affects the effect, ie the generation of uniform cells.

The polypropylene resin foam of the present invention is
It is a thick-plate polypropylene resin foam having a density of 0.02 to 0.05 g / cm ³ and a thickness of 10 mm or more, preferably 15 mm or more. It should be noted that the thick one is 1
It is possible to manufacture even a thickness of about 00 mm without any problem. The slab-like polypropylene resin foam having such a density and thickness is a new one which has never been obtained.

The density is the value obtained by dividing the weight of the foam by its submerged volume, and the thickness is the length of the short side of the slab-shaped rectangular foam, which is non-rectangular. By the way, in the cross section, it means the shortest length between the vertices and the sides, or the shortest length between the parallel planes, if any.

As a method for obtaining a polypropylene resin having a melt tension of 3 g or more and a difference ΔT between the melting point and the crystallization temperature of 40 ° C. or less used in the present invention, as long as such a polypropylene resin can be obtained, There is no limitation, but specific methods include, for example, polypropylene having free-end long-chain branching and imparting strain hardening elongation viscosity, a method of mixing polypropylene with a polyolefin such as polyethylene, and other methods of polypropylene. The method of copolymerizing polyolefins, the method of mixing polypropylene with a substance exhibiting a fibril structure when mixed, for example, polytetrafluoroethylene, or the like, or various inorganic substances and crystallization for the purpose of controlling material properties and crystallization characteristics of polypropylene. Examples include a method of mixing a nucleating agent.

The above-mentioned method for imparting strain hardening elongation viscosity to polypropylene having free-end long-chain branching is
According to Japanese Unexamined Patent Publication (Kokai) No. 62-121704, high energy ionizing radiation is applied to polypropylene having no strain hardening elongation viscosity for a time sufficient for chain scission, but not for gelling of polypropylene. hand,
Further, the treatment is performed so that long-chain branching is generated, and then a treatment for deactivating all free radicals present in the irradiated polypropylene is carried out. By this method, polypropylene having a melt tension of 3 g or more and a difference ΔT between the melting point and the crystallization temperature of 40 ° C. or less can be obtained.

The method of mixing the polyolefin with the polypropylene is MI 0.1 to 30, preferably 0.1.
For linear polypropylene having a density of 3 to 20, for example, low density polyethylene having a density of 0.910 to 0.924 g / cm ³ or density of 0.941 to 0.965 g / cm ^3.
cm ³ of polyolefin such as high density polyethylene is 0.1 to 50% (wt%, the same applies hereinafter), preferably 1 to
This is a method of kneading with a 20% dry blend or a twin-screw extruder.

By this method, a polypropylene resin having a melt tension of 3 g or more and a difference ΔT between the melting point and the crystallization temperature of 40 ° C. or less can be obtained.

The method of copolymerizing the above polypropylene with other polyolefin means that 1 to 5% of olefin such as ethylene is added to linear polypropylene having MI of 0.1 to 30, preferably 0.3 to 20. This is a method in which block copolymerization or graft copolymerization is performed at a certain ratio.

By this method, a polypropylene resin having a melt tension of 3 g or more and a difference ΔT between the melting point and the crystallization temperature of 40 ° C. or less can be obtained.

The method of mixing a substance having a fibril structure when mixed with the polypropylene is MI 0.1.
~ 30, preferably about 0.3 to 20 linear polypropylene, for example, polytetrafluoroethylene, etc., 0.01 to 10%, preferably about 0.1 to 3% dry blend or twin-screw extruder. It is a method of kneading.

By this method, a polypropylene resin having a melt tension of 3 g or more and a difference ΔT between the melting point and the crystallization temperature of 40 ° C. or less can be obtained.

The method of mixing various inorganic substances and crystallization nucleating agents with the above polypropylene for the purpose of controlling material properties and crystallization properties is MI 0.1 to 30, preferably 0.3 to 20.
For linear polypropylene of a certain degree, for example, inorganic substances such as calcium carbonate and talc, aluminum hydroxydipara-t-butylbenzoate, dibenzylidene sorbitol, dimethyl benzylidene sorbitol, 2,2-methylenebis (4,6-diphenyl phosphate) 0.1 to 1 of an organic crystallization nucleating agent such as -t-butylphenyl) sodium.
It is a method of kneading with 0%, preferably 0.1 to 5% by dry blending or a twin-screw extruder.

The polypropylene resin foam of the present invention as described above has a specific melt tension and a specific ΔT as described above.
A polypropylene-based resin having, for example, 100 parts of the polypropylene-based resin, 10 to 25 parts of a foaming agent, preferably 10 to 15 parts, and 0.01 to 1.0 part of a foam nucleating agent,
Preferably 0.1 to 0.5 parts are melt mixed in an extruder,
What is kept at high pressure is 5 to 2 than Tm in the formula (1).
It is produced by keeping the temperature at 5 ° C. low, then extruding it out of the extruder, and rapidly cooling and crystallizing the extrudate in a plastic state in the process of growing bubbles inside the extruded mixture.

Polypropylene resin 1 in the above method
A large amount of the foaming agent is added to 00 parts to 10 to 25 parts because, in addition to foaming the polypropylene-based resin, the heat of vaporization from the polypropylene-based resin being foamed during extrusion foaming This is because a high-magnification foam can be obtained by cooling from the above to solidify the cell wall and hold the foaming agent turned into gas therein. That is,
Polypropylene resin has a high degree of crystallinity and the amount of heat generated during crystallization is large, which prevents cooling from the outside of the foam and eventually solidification of the cell walls, destroying the cells of the polypropylene resin in the process of foaming. Easy to do and transform. Therefore, by adding a large amount of the foaming agent, the temperature of the polypropylene-based resin in the process of foaming is rapidly reduced by utilizing the latent heat cooling when the foaming agent is vaporized to fix the cell wall. Therefore, the amount of the foaming agent required is 10 parts or more with respect to 100 parts of the polypropylene resin, and if the amount is less than that, the effect of cooling the polypropylene resin by the heat of vaporization cannot be expected. On the other hand, if it exceeds 25 parts, the foaming agent may be ejected from the die at the time of extrusion, so that the operating condition is not stable, and it becomes difficult to produce a good foam.

In the present invention, the molten mixture of the polypropylene resin, the foaming agent and the foam nucleating agent is kept at a temperature 5 to 25 ° C. lower than the melting peak temperature Tm of the polypropylene resin before being extruded out of the extruder. It is necessary to lower the temperature of the mixture in the extruder to cool and crystallize more quickly when the polypropylene resin in the non-crystallized or semi-crystallized state is extruded out of the extruder. This is because the melting tension of the molten mixture is maintained and the retaining property of the foaming agent is maintained by decreasing the temperature of the molten mixture.

Even if the mixture is cooled to a temperature below the melting point of the polypropylene resin in the extruder, a large amount of the blowing agent is kneaded at a high pressure so that the mixture has a freezing point lowering action and a crystallization inhibiting action. By constantly receiving mechanical energy from the machine screw,
Maintains fluidity without solidification or crystallization. If the temperature of the mixture in this extruder is higher than 5 ° C., which is lower than the Tm of the polypropylene resin, the viscoelasticity of the polypropylene resin in the mixture does not reach a region sufficient to hold the cell walls, and If the temperature of the mixture in the extruder is lower than the Tm of polypropylene resin, 25 ° C or lower, the crystallization occurs in the extruder or the resin is added to the die part when the mixture is extruded from the extruder. The result is that the operating state during extrusion is not stable, such as clogging, and a good foam cannot be manufactured.

As the foaming agent, a volatile foaming agent, an inorganic foaming agent, or a decomposable foaming agent can be used.

Specific examples of the volatile blowing agent include aliphatic hydrocarbons such as propane, n-butane, i-butane, pentane and hexane, and cycloaliphatic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane. Trichlorofluoromethane, dichlorodifluoromethane,
Examples thereof include halogenated hydrocarbons such as dichlorotetrafluoroethane, methyl chloride, ethyl chloride and methylene chloride.

Specific examples of the inorganic foaming agent include:
Examples include carbon dioxide, air, and nitrogen.

Further, specific examples of the decomposition type foaming agent include azodicarbonamide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, sodium bicarbonate and the like.

These foaming agents may be used in combination.

The amount of the foam nucleating agent used is 0.01.
If the amount is less than the range, the bubbles generated become coarse and it becomes difficult to form a uniform foam. On the other hand, if it exceeds 1.0 part, the thickness of the cell membrane becomes thin, and the cells are likely to be broken or open, and it becomes difficult to obtain a good foam.

Specific examples of the foam nucleating agent include a reaction product of a polyvalent carboxylic acid such as citric acid and sodium carbonate or sodium bicarbonate, an acid salt of the polyvalent carboxylic acid, or an inorganic powder such as talc or silica. And the like are preferred.

Furthermore, if necessary, a heat stabilizer, an ultraviolet absorber, an antioxidant and the like may be added.

To maintain the polypropylene resin, the foaming agent and the foam nucleating agent at a high pressure when melt-mixed in an extruder means that the foaming agent is dissolved in the polypropylene resin in a molten state and the foaming agent is It means a state of being held so as not to dissociate from the melt-mixed state.

Further, to rapidly cool and crystallize the extrudate in a plastic state in the process of growing bubbles inside the mixture extruded to the outside of the extruder means that the mixture held at a high pressure is in a low pressure region. It is extruded, the foaming agent expands with the change in pressure, bubbles grow, and the foaming agent volatilizes from the extrudate, so that the expansion and volatilization of these foaming agents cause rapid cooling and crystallization. means.

By such a method, it becomes possible to provide a thick plate-shaped polypropylene resin foam excellent in quality, which has been difficult in the past, and has an extremely high industrial value.

The present invention will be described in more detail based on the following examples.

Table 1 shows the physical properties of the polypropylene resins used in Examples and Comparative Examples.

For measuring the melt tension of the polypropylene resin used, a capillograph manufactured by Toyo Seiki Seisaku-sho, Ltd. was used, and for measuring Tm and Tcc, a DSC200 manufactured by Seiko Denshi Kogyo Co., Ltd. was used. It measured like this.

[0051]

[Table 1]

Example 1 Polypropylene (PF-814 manufactured by Highmont Co., Ltd., having free-end long-chain branching according to the production method disclosed in Japanese Patent Laid-Open No. 62-121704, and having strain hardening elongation viscosity. To 100 parts of polypropylene), 0.1 part of Super Ease (manufactured by Koshigaya Kasei Co., Ltd.) was added as a blended oil and mixed with a ribbon blender. ) Cervon SG / K) 0.5 part was added and mixed again with a ribbon blender, and a extruder with a diameter of 40 mm and a diameter of 50 mm was used.
The discharge amount shown in Table 2 was supplied to an extruder connected to the extruder.

The mixture supplied to the extruder having a diameter of 40 mm was heated to 230 ° C., melted and kneaded, and from the vicinity of the tip of the extruder having a diameter of 40 mm, a mixture of isorich butane (85% isobutane and 15% normal butane) as a foaming agent was mixed. ) Was pressed and mixed in a ratio of 15 parts to 100 parts of polypropylene. The temperature of the mixture is adjusted to 14 with an extruder with a diameter of 50 mm.
Adjust the temperature to 9 ° C and adjust so that the pressure of about 20 kg / cm ² is applied to the mouthpiece (the tip has a thickness of 0.6 mm and a width of 60 mm.
mm discharge outlet). The mixture extruded from the die greatly foamed and was formed into a plate shape by a molding die.

The discharge rate from the extruder was 6.1 kg / h, and the extrusion was carried out stably without fluctuation of the discharge rate and without clogging of the die with resin (extrusion stability). Evaluate as ○). Further, the thickness and density of the obtained plate-like foam were measured by the following methods. Table 2 shows the results
Shown in

The temperature of the mixture (represented by Tre) at the tip of the extruder having a diameter of 50 mm is 149 ° C., and the melting peak temperature Tm of polypropylene is 162 ° C. Therefore, the temperature difference Tre−Tm is −13 ° C. Met.

Table 2 collectively shows the Tre, Tre-Tm, the amount of the foaming agent, the amount of the foam nucleating agent, and the discharge amount.

(Thickness of Plate-shaped Foam) The length of the short side of the obtained plate-shaped foam was measured and defined as the thickness.

(Density of Plate Foam) A small piece (about 10 cc) was taken from the plate foam, the weight was measured, and the submerged volume was measured to calculate the density.

Example 2 The mixture temperature in a 50 mm extruder was set at 145 ° C.,
Except foaming was carried out in substantially the same manner as in Example 1 except that Tre-Tm was changed to -17 ° C. and the amount of the foaming agent added was changed to 12 parts based on 100 parts of polypropylene to produce a plate-shaped foam.

Extrusion stability, as in the case of Example 1,
The thickness and density of the plate-like foam were evaluated. The results are shown in Table 2 together with the foaming conditions.

Example 3 Set the mixture temperature in a 50 mm extruder to 142 ° C.,
Except foaming was carried out in the same manner as in Example 1 except that Tre-Tm was changed to -20 ° C, and the amount of the foaming agent added was changed to 12 parts based on 100 parts of polypropylene to produce a plate-like foam.

In the same manner as in Example 1, the extrusion stability, the thickness and the density of the plate-like foam were evaluated. The results are shown in Table 2 together with the foaming conditions.

Example 4 The mixture temperature in a 50 mm extruder was set to 139 ° C.,
The value of Tre-Tm was changed to -23 ° C, and the amounts of the foaming agent and the nucleating agent added were 12 per 100 parts of polypropylene.
Parts and 0.1 parts, except that extrusion foaming was performed in the same manner as in Example 1 to produce a plate-shaped foam.

In the same manner as in Example 1, the extrusion stability, the thickness and density of the plate-like foam were evaluated. The results are shown in Table 2 together with the foaming conditions.

Example 5 Block copolymer of polypropylene and polyethylene (polyethylene content about 3%, SD-6 manufactured by Highmont Co., Ltd.)
13) was used and the mixture temperature in a 50 mm extruder was 1
Extrusion foaming was carried out in substantially the same manner as in Example 1 except that the temperature was set to 48 ° C, the Tre-Tm was changed to -12 ° C, and the addition amount of the foaming agent was changed to 14 parts relative to 100 parts of the resin. The body was made.

Extrusion stability, plate-like foam thickness and density were evaluated in the same manner as in Example 1. The results are shown in Table 2 together with the foaming conditions.

Example 6 Block copolymer of polypropylene and polyethylene (polyethylene content of about 3%, SD-6 manufactured by Highmont Co., Ltd.
13) was used and the mixture temperature in a 50 mm extruder was 1
Extrusion foaming was performed in substantially the same manner as in Example 1 except that the temperature was set to 44 ° C., the Tre-Tm was changed to −16 ° C., and the addition amount of the foaming agent was changed to 12 parts with respect to 100 parts of the resin. The body was made.

Extrusion stability, the thickness and the density of the plate-like foam were evaluated in the same manner as in Example 1. The results are shown in Table 2 together with the foaming conditions.

Example 7 Block copolymer of polypropylene and polyethylene (polyethylene content about 3%, SD-6 manufactured by Highmont Co., Ltd.
13) was used and the mixture temperature in a 50 mm extruder was 1
Extrusion foaming was performed in substantially the same manner as in Example 1 except that the temperature was set to 43 ° C., Tre-Tm was changed to −17 ° C., and the addition amount of the foaming agent was changed to 20 parts with respect to 100 parts of the resin. The body was made.

Extrusion stability, the thickness and the density of the plate-like foam were evaluated in the same manner as in Example 1. The results are shown in Table 2 together with the foaming conditions.

Example 8 Block copolymer of polypropylene and polyethylene (polyethylene content about 3%, SD-6 manufactured by Highmont Co., Ltd.
13) was used and the mixture temperature in a 50 mm extruder was 1
Example 1 except that the temperature was set to 38 ° C., the Tre-Tm was changed to −22 ° C., and the amounts of the foaming agent and the foam nucleating agent added were changed to 20 parts and 0.1 parts, respectively, relative to 100 parts of the resin. Extrusion foaming was carried out almost in the same manner to produce a plate-shaped foam.

In the same manner as in Example 1, the extrusion stability, the thickness and density of the plate-like foam were evaluated. The results are shown in Table 2 together with the foaming conditions.

Comparative Example 1 The mixture temperature in a 50 mm extruder was set to 145 ° C.,
Except foaming was carried out in the same manner as in Example 1 except that Tre-Tm was changed to -17 ° C, and the amount of the foaming agent added was changed to 2 parts based on 100 parts of polypropylene to produce a plate-like foam.

Extrusion stability, the thickness and the density of the plate-like foam were evaluated in the same manner as in Example 1. The results are shown in Table 3 together with the foaming conditions.

From Table 3, it can be seen that the foam is extruded stably, but the density is 0.093 g / cm ³ , and only a foam having a low magnification is obtained.

Comparative Example 2 The mixture temperature in a 50 mm extruder was set to 148 ° C,
Tri-Tm was changed to -14 ° C., and the addition amount of the foaming agent was changed to 29 parts based on 100 parts of polypropylene. Extrusion foaming was carried out in the same manner as in Example 1 to produce a plate-shaped foam. However, since the foaming agent was ejected from the die during extrusion, it could not be stably extruded and a normal foam could not be obtained.

Comparative Example 3 The mixture temperature in a 50 mm extruder was set at 170 ° C.,
Except foaming was carried out in the same manner as in Example 1 except that Tre-Tm was changed to + 8 ° C., and the amount of the foaming agent added was changed to 10 parts based on 100 parts of polypropylene to produce a plate-shaped foam.

As in the case of Example 1, extrusion stability,
The thickness and density of the plate-like foam were evaluated. The results are shown in Table 3 together with the foaming conditions.

From Table 3, it can be seen that the foam is stably extruded, but the density is 0.180 g / cm ³ , and only a foam having a low magnification is obtained.

Comparative Example 4 The mixture temperature in a 50 mm extruder was set to 127 ° C.,
Except foaming was carried out in the same manner as in Example 1 except that Tre-Tm was changed to -35 ° C. and the amount of the foaming agent added was changed to 18 parts with respect to 100 parts of polypropylene to prepare a plate-shaped foam. During extrusion, the spinneret was clogged with resin and the operating condition of the extruder became unstable.

Extrusion stability, as in the case of Example 1,
The thickness and density of the plate-like foam were evaluated. The results are shown in Table 3 together with the foaming conditions.

From Table 3, it can be seen that the density was 0.228 g / cm ³ , and only a foam having a low magnification was obtained.

Comparative Example 5 The mixture temperature in a 50 mm extruder was set to 163 ° C.,
Example 1 except that Tre-Tm was changed to + 1 ° C. and the amount of the foaming agent added was changed to 2 parts based on 100 parts of polypropylene.
Extrusion foaming was carried out almost in the same manner as above to produce a plate-like foam.

Extrusion stability, as in Example 1
The thickness and density of the plate-like foam were evaluated. The results are shown in Table 3 together with the foaming conditions.

From Table 3, it can be seen that the foam is stably extruded, but the density is 0.144 g / cm ³ , and only a foam having a low magnification is obtained.

Comparative Example 6 The mixture temperature in a 50 mm extruder was set at 133 ° C.,
Except foaming was carried out in the same manner as in Example 1 except that Tre-Tm was changed to -29 ° C., and the amount of the foaming agent added was changed to 3 parts based on 100 parts of polypropylene. During extrusion, the die was clogged with resin, the operating state of the extruder became unstable, and the state of the foam was not constant.
The density of the foam was 0.350 g / cm ³ , and only a foam having a low magnification was obtained. The results are shown in Table 3.

Comparative Example 7 The mixture temperature in a 50 mm extruder was set at 169 ° C.
Except that the re-Tm was changed to + 7 ° C. and the amount of the foaming agent added was 28 parts relative to 100 parts of polypropylene, extrusion foaming was carried out in the same manner as in Example 1 to prepare a plate-like foam. The extrusion stability was unstable, such as the blowing agent spouting from the die. The density of the foam is 0.075g
/ Cm ³ , and only a foam having a low magnification was obtained.
The results are shown in Table 3.

Comparative Example 8 Mixture temperature in a 50 mm extruder was set to 132 ° C.,
Except foaming was carried out in the same manner as in Example 1 except that Tre-Tm was changed to -32 ° C., and the amount of the foaming agent added was changed to 27 parts based on 100 parts of polypropylene. During extrusion, the die was clogged with resin, the operating state of the extruder became unstable, and the state of the foam was not constant. Further, the density of the foam was 0.325 g / cm ³ , and only a foam having a low magnification was obtained. The results are shown in Table 3.

Comparative Example 9 Using polypropylene (Noblene Z101A manufactured by Sumitomo Chemical Co., Ltd.) having a low melt tension value of 0.4 g, the mixture temperature in a 50 mm extruder was set to 149 ° C., and Tre-Tm was set. Was changed to −14 ° C. and the amount of the foaming agent was changed to 14 parts with respect to 100 parts of polypropylene, and extrusion foaming was performed in substantially the same manner as in Example 1 to produce a plate-shaped foam.

As in Example 1, extrusion stability,
The thickness and density of the plate-like foam were evaluated. The results are shown in Table 3 together with the foaming conditions.

From Table 3, it can be seen that the foam is stably extruded, but the density is 0.421 g / cm ³ , and only a foam having a low magnification is obtained.

Comparative Example 10 Polypropylene (Nobrene D501 manufactured by Sumitomo Chemical Co., Ltd.) having a large difference between the melting peak temperature Tm and the crystallization peak temperature Tcc of 51 ° C. was used, and the mixture temperature in a 50 mm extruder was 151. Set to ℃, Tre-Tm -12
Extruded foaming was carried out in substantially the same manner as in Example 1 except that the amount of the foaming agent added was changed to 12 parts with respect to 100 parts of polypropylene instead of 100 ° C. to produce a plate-like foam.

As in the case of Example 1, extrusion stability,
The thickness and density of the plate-like foam were evaluated. The results are shown in Table 3 together with the foaming conditions.

From Table 3, it can be seen that the foam is extruded stably, but the density is 0.280 g / cm ³ , and only a foam having a low magnification is obtained.

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[Table 2]

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[Table 3]

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EFFECTS OF THE INVENTION When a thick plate-shaped polypropylene resin foam is manufactured by the conventional external cooling method, cell fusion or cell breakage occurs, and a good low-density thick plate foam cannot be obtained. However, according to the method of the present invention, it is possible to obtain a low-density, thick-plate-shaped polypropylene resin foam having good cells. This thick-plate polypropylene resin foam is a new product that has not existed in the past.

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Claims (2)

[Claims] 1. Melt tension (melt tension) is 3 g or more, and formula (1): ΔT = Tm-Tcc (1) (wherein, Tcc is a polypropylene resin in a nitrogen atmosphere, differential scanning Heating rate 10 ° C by calorimetric analyzer
After heating and melting up to 200 ° C at 10 / min, 10 ° C
The crystallization peak temperature, Tm, detected in the process of cooling to room temperature at 10 min / min is the melting peak temperature detected in the process of heating the cooled resin again to 200 ° C. at a temperature rising rate of 10 ° C./min. ), A density of 0.02 to 0.
A slab-like polypropylene resin foam having a thickness of 05 g / cm ³ and a thickness of 10 mm or more. 2. When extrusion-molding a polypropylene resin, the melt tension is 3 g or more, and the formula (1): ΔT = Tm-Tcc (1) (where Tcc is: Polypropylene resin in nitrogen atmosphere with a differential scanning calorimetry analyzer temperature rising rate of 10 ° C / m
After heating and melting up to 200 ° C in in, 10 ° C / m
The crystallization peak temperature, Tm, detected in the process of cooling to room temperature with in is the rate of temperature increase of 10 for the cooled resin again.
(That is the melting peak temperature detected in the process of heating to 200 ° C. at a heating rate of 100 ° C./min) 100 parts by weight of polypropylene resin having ΔT of 40 ° C. or less, and blowing agents 10 to 25
Parts by weight and 0.01 to 1.0 parts by weight of a foam nucleating agent, the temperature of the molten mixture kept at a high pressure in an extruder is maintained at a temperature 5 to 25 ° C. lower than Tm in the formula (1). Then, extruded out of the extruder, rapidly cooling and crystallizing the extruded product in the plastic state in the process of growing bubbles inside the extruded mixture, density 0.02-0.05 g / cm ³ , thickness A method for producing a polypropylene resin foam having a thickness of 10 mm or more.