JPH05293903A - Highly foamed sheet of non-crosslinked polypropylenebased resin and production thereof - Google Patents

Abstract

PURPOSE:To enhance secondary workability such as vacuum thermoforming by using a foamed sheet which shows a specified endothermic peak in the prescribed DSC curve and has specified plane smoothness for the highly foamed sheet of non- crosslinked polypropylene-based resin wherein the rate of a closed cell and bulk density show the specified value respectively. CONSTITUTION:A foamed sheet is raised in temperature to 200 deg.C from room temperature at 10 deg.C/minute temperature rise velocity by a differential scanning calorimeter. A cure obtained in this case is defined as the DSC curve of a first time. The foamed sheet is lowered in temperature to 40 deg.C from 200 deg.C at 5 deg.C/minute temperature drop velocity and again similarly raised in temperature to 200 deg.C. A curve obtained in this case is defined as the DSC curve of a second timed When the curves are defined in such a way, the following foamed sheet is used for the highly foamed sheet of non-crosslinked polypropylene-based resin which has >=90% rate of closed cell, 0.20-0.15g/cm<3> bulk density and 1-10mm thickness. In the foamed sheet, at least two or more endothermic peaks show 140-165 deg.C and the difference of temperature of the respective vertexes of the endothermic peaks in the low temperature side and the high temperature side is 5 deg.C or above and also the value of plane smoothness is 0.02 or below.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a problem of waste of a crosslinked highly foamed sheet, and relates to a non-crosslinked polypropylene resin highly foamed sheet which has hitherto been impossible to realize and a manufacturing method thereof. is there. More specifically, a new and highly useful non-crosslinked polypropylene resin having excellent properties comparable to those of the high-expanded crosslinked polypropylene sheet, which could not be obtained by the conventional non-crosslinked polypropylene extruded high foamed sheet. The present invention relates to a foamed sheet and a method for manufacturing the same.

[0002]

2. Description of the Related Art Polyolefin high-foamed sheets are excellent in mechanical strength, flexibility, heat resistance, chemical resistance, and light weight, and are used in a wide range of applications such as vehicles, heat insulation industry, packaging and packaging fields. .. Among them, the polyethylene high-foamed sheet is excellent in flexibility and elongation due to its low melting point, whereas the polypropylene high-foamed sheet is excellent in mechanical strength such as tensile strength and bending strength and heat resistance. On the other hand, however, polypropylene resins are crystalline polymers, and when heated above the melting temperature, the viscosity decreases sharply, so the temperature range for viscoelasticity suitable for foaming is narrow, and it is possible to obtain foams with a high expansion ratio. There was the problem of being extremely difficult.

In order to solve the above-mentioned problems, for example, in Japanese Patent Publication No. 42-26953, radiation is irradiated at the time of manufacturing a polypropylene resin foam sheet to appropriately crosslink the material to reduce the temperature dependence of melt viscosity. A method of doing so has been proposed and is currently being industrially implemented and completed.

This cross-linking technique is originally known as a means for modifying resin properties, and polypropylene resin is mixed with other resin components such as polystyrene to coexist to modify the properties of the resin. Compared with the above means, there is an advantage that the original characteristics of the polypropylene resin are not impaired. The cross-linked polypropylene-based resin high-foaming sheet obtained by the chemical foaming method has excellent secondary processability such as thermo-vacuum moldability and has a smooth surface. Widely used in food packages for microwave ovens.

However, this polypropylene resin cross-linking means requires an extra step for cross-linking, so that the equipment cost and energy expenses are relatively large, and even if the cross-linked foamed sheet becomes unnecessary, There is an economically disadvantageous problem in that it cannot be returned to the resin and used for recovery. In particular, as the global environmental problem (waste treatment) is severely demanded, it is strongly desired to develop a technology regarding a high-foaming polypropylene resin sheet in which a crosslinking step is omitted.

As a non-crosslinked polypropylene resin foam sheet corresponding to this, a foam sheet obtained by an extrusion foaming method is known. For example, JP-A-49-11876
No. 4 (a method of extruding a mixture of 50 to 90% by weight of crystalline polypropylene, 10 to 50% by weight of an ethylene-propylene random copolymer and a chemical foaming agent in a sheet form by heating) and JP-A-60-31538 ( Propylene homopolymer or propylene-ethylene block copolymer 5
2 to 97% by weight and a propylene-α-olefin copolymer of 3 to 48% by weight, melt-kneaded with a foaming agent, and then extrusion foaming. There is described a method for obtaining a foamed sheet having a certain low expansion ratio (6 cc / g or less, that is, an apparent density of 0.167 g / cc or more).

Further, JP-A-58-49730 (Propylene-ethylene block copolymer 80 to 99% by weight and propylene-ethylene-butene ternary random copolymer 1)
~ 20 wt% of the mixture is melt-kneaded with a blowing agent and then extrusion foaming) and JP-A-62-192430 (propylene homopolymer and / or ethylene-propylene block copolymer 30-95 wt% and ethylene). -Propylene Random Copolymer A mixture of 5 to 70% by weight is melt-kneaded with a foaming agent, and then extrusion foaming is disclosed in a publication of high expansion ratio (30 to 70 cc / g, that is, apparent density of 0.01).
A method for obtaining a foamed sheet of 4 g / cc to 0.033 g / cc) is described.

These extrusion foaming methods solve the drawback of narrowing the proper foaming temperature range, which is a problem when a polypropylene resin foam is produced by mixing a random propylene resin having a low melting point. The purpose is to sufficiently develop and provide the excellent physical properties possessed.

[0009]

However, in the above-mentioned invention using the extrusion foaming method, it has flexibility like a cross-linked high-foaming sheet, has a smooth surface, is aesthetic, and has a hot vacuum forming secondary processability. The problem still remains that a high-foaming sheet cannot be obtained. The cause of this is that the extrusion foaming method is a method in which the foaming agent is homogeneously mixed in a high temperature and high pressure state, then cooled to near the melting point, and extruded into the air from a die attached to the tip of the extruder to generally foam, which is an essential difficulty. It is believed that there is.

That is, i) In the case of the low-foamed sheet of the above publication, the foaming rate during extrusion foaming is relatively slow and the buckling strength of the sheet is high, so that a foamed sheet having a smooth surface can be easily produced. In the case of the high-foaming sheet of the above-mentioned publication, the resin has a high foaming speed and is rapidly stretched, and the restraining force of the unfoamed portion (the force of spreading in three dimensions) against the instantaneous large strain change. This is a problem that only a foamed sheet having a smooth surface with a wavy surface and poor cosmetic appearance is obtained.

As a solution to this problem, a volatile foaming agent having a high solubility or a high boiling point is used to slow the foaming rate, but this produces a coarse bubble diameter and, conversely, deteriorates the cosmetic appearance. To do. In addition, various methods have been tried such as forming an extruded bubble from an annular slit die and injecting a pressurized gas (air, etc.) into the bubble to perform foam molding, but with a highly foamed product (6 cc / g or more), it is smooth. Only a foamed sheet with poor beauty is obtained. ii) A high-foaming sheet having a high closed cell rate is obtained by crystallizing and immobilizing the molten resin that forms a cell film by heat absorption due to evaporation of the foaming agent in the cell growth process.

However, the polypropylene resin has a drawback that the crystallization rate is extremely slow, so that the foam film cannot be fixed by crystallization only by the latent heat of vaporization of the foaming agent. A foamed sheet having a high closed cell rate is obtained by extrusion foaming at a foaming temperature below the melting point of the resin.

Although the proper foaming temperature range can be widened by mixing a random propylene resin having a low melting point,
The foaming temperature shifts to the low temperature side by a small amount. On the contrary, the condition of the foaming temperature equal to or lower than the melting point causes crystallization and outflow in the retention part such as the inner wall surface of the die, and as a result, surface cracks are apt to occur and lack flexibility, or the surface of the foamed sheet is dented, The problem is that cracks occur and a quality foam sheet cannot be made.

Since these problems have not been solved yet, it is impossible to produce a highly foamed sheet having excellent secondary workability in thermal vacuum forming. As a result, it is limited to packaging materials that have low requirements for thermoformability and surface appearance quality. It is speculated that this is the reason why it is not possible to enter the fields of vehicles and heat insulation as a substitute for high value-added crosslinked and highly foamed sheets.

In view of the above situation, the inventors of the present invention have conducted a long-term study on an optimal foaming method capable of exhibiting excellent properties like a crosslinked foamed sheet without crosslinking, and as a result, the conventional noncrosslinked polypropylene resin has been obtained. It succeeded in obtaining a non-crosslinked highly foamed sheet which is flexible, has a smooth surface, and has cosmetic properties as compared with an extruded foamed sheet product. And, surprisingly, the fact that the non-crosslinked high-foamed sheet completed in the present invention is a high-foamed sheet having a thermal vacuum forming secondary processability comparable to that of the crosslinked high-foamed sheet was found, Is the completion of.

Therefore, the object of the present invention is to produce a high-foaming sheet having a surface smoothness and cosmetics superior to that of a conventional extruded high-foaming sheet by using a non-crosslinked polypropylene resin which clears the waste problem. It is to provide a method, and to provide a non-crosslinked polypropylene-based resin highly foamed sheet which is excellent in hot vacuum forming secondary processability.

[0017]

The above object of the present invention is to provide a foamed sheet of the present invention, that is, a closed cell ratio of 90% or more, an apparent density of 0.020 to 0.15 g / cm ³ , and a thickness of 1 to 10.
mm non-crosslinked polypropylene-based resin high foamed sheet, the foamed sheet was obtained by differential scanning calorimetry at the second DSC curve (however, 3-5 mg of foamed sheet from room temperature to 200 ° C at 10 ° C / 200 ° C). The curve obtained when the temperature was raised at a heating rate of
C curve, then the temperature was lowered from 200 ° C. to 5 ° C./min to 40 ° C., and again to 10 ° C./min to 200 ° C.
The curve obtained when the temperature is raised to 0 ° C is referred to as the second DSC curve), and at least two or more endothermic peaks are shown in the temperature range of 140 to 165 ° C. And the temperature at the apex of the endothermic peak on the high temperature side is 5 ° C. or more, and the value of the surface smoothness (flat S) obtained by the following method is 0.02 or less. Highly foamed polypropylene resin sheet.

The surface smoothness (flat S) is the ratio of measurement at one location over the entire length in the width direction of the foamed sheet, which is 150 mm in length in the width direction. Is measured, and the obtained value S is shown as an average value at 10 points.

The measurement is carried out on a small sheet (200 mm in width direction).
× Flow direction length 50 mm) is placed on a chamber having a smooth surface plate made of sintered metal on the upper surface, vacuum suction is applied to one side of the sheet to the surface plate, and a roller attached to the surface plate ( (Outer diameter 22 mm, width 7 mm) Type thickness gauge is run in the width direction of 150 mm excluding 25 mm at both ends of the small piece sheet,
The minimum reading is a value obtained by continuously measuring and recording the thickness in units of 0.01 mm. And on this measured and recorded thickness data curve, divide from a mountain to the next valley, and from that valley to the next mountain,
The maximum value calculated by the following formula is adopted by reading the thickness difference (ΔT: mm) between the peak and the valley and the span length (L: mm) for each division.

[0020]

## EQU00003 ## S = .DELTA.T / L This operation is repeated at the above 10 points. And the manufacturing method of the present invention, that is, the closed cell ratio is 90% or more, and the apparent density is 0.020 to 0.1.
In the method for producing a non-crosslinked polypropylene-based resin high-foaming sheet having a thickness of 1 to 10 mm at 5 g / cm ³ , the endothermic peak by differential scanning calorimetry (heating rate 10 ° C./min) is 135 to 1.
Random copolymerized polypropylene resin (A) 55 to 95% by weight with an α-olefin having 2 to 20 carbon atoms at 50 ° C., and a polypropylene homopolymer having an endothermic peak higher than that of the random copolymer by 10 ° C., ethylene. Of block copolymer polypropylene resin, and one or more combination resins (B) of 45 to 45% by weight of a random copolymer polypropylene resin with an α-olefin having 2 to 20 carbon atoms, and a mixed resin. The mixture is melt-kneaded through an extruder and extruded into a sheet, the volatile foaming agent or the inorganic gas is impregnated into the sheet, and the steam is heated at a temperature lower than the melting point of the resin (B) to 0.2 to 1.0 times / Foam at a foaming speed of seconds,
A surface-smoothness (flat S) obtained by the following method is 0.02 or less.

The surface smoothness (flat S) is the ratio of measurement at one location over the entire length in the width direction of the foamed sheet, which is 150 mm in the width direction, and the following is obtained for 10 random locations in the width direction at intervals of 100 mm in the flow direction. Is measured, and the obtained value S is shown as an average value at 10 points.

The measurement is carried out on a small piece sheet (widthwise length 200 mm
× Flow direction length 50 mm) is placed on a chamber having a smooth surface plate made of sintered metal on the upper surface, vacuum suction is applied to one side of the sheet to the surface plate, and a roller attached to the surface plate ( (Outer diameter 22 mm, width 7 mm) Type thickness gauge is run in the width direction of 150 mm excluding 25 mm at both ends of the small piece sheet,
The minimum reading is a value obtained by continuously measuring and recording the thickness in units of 0.01 mm. And on this measured and recorded thickness data curve, divide from a mountain to the next valley, and from that valley to the next mountain,
The maximum value calculated by the following formula is adopted by reading the thickness difference (ΔT: mm) between the peak and the valley and the span length (L: mm) for each division.

[0023]

## EQU00004 ## S = .DELTA.T / L This operation is repeated at the above 10 points. Can be easily achieved.

The contents of the present invention will be described in detail below with reference to the drawings according to the constituent features of the invention. FIG. 1 shows a non-crosslinked highly foamed sheet of the present invention (obtained by the method of the present invention of Experiment No. 1),
FIG. 2 shows a non-crosslinked high-foaming sheet of a comparative product (obtained by the extrusion foaming method of Experiment No. 33), both of which are conceptual sketches of local enlargement of the cross section in the width direction of the foaming sheet.

1 and 2 are common in that they are both highly foamed sheets having the same composition of polypropylene resin as the base resin. These two types of foamed sheets have a high closed cell rate (90% or more), are excellent in mechanical strength and compression recovery, and can be practically used as a cushioning packaging material.

Comparing the structural characteristics of the above-mentioned type 2 foamed sheet with the comparison of FIGS. 1 and 2, the foamed sheet of the present invention (FIG. 1) has uniform cell diameters in the width direction and a relatively smooth surface. Compared with the state, the foam sheet of the comparative product (FIG. 2) is randomly arranged such that the cell diameter in the vicinity of the surface in the width direction is a cell group having a small diameter and a cell group having a large diameter.
Moreover, it is well understood that the surface is wavy and lacks in smoothness. The cause of the smooth state of the surface and the uniform state of the bubble diameter in the width direction are both the same, and it is presumed to be an abnormal phenomenon due to a local viscoelastic change with respect to strain change (external reaction force) during foaming. To be done.

Therefore, it was devised to make a coefficient into a structure capable of distinguishing the structural difference from the conventional non-crosslinked high-foamed sheet product and expressing the characteristics of the non-crosslinked high-foamed sheet product of the present invention. That is, it has a "surface smoothness (flat S) of 0.02" which is a main requirement of the non-crosslinked high-foamed sheet of the present invention.
Below is a structural index.

First, a method of obtaining the surface smoothness (flat S) itself will be described. FIG. 4 shows sampling positions of measurement points of the foamed sheet, and an arbitrary width-direction total length line: a width-direction length of 200 mm and a flow-direction length of 50 mm at an arbitrary position with A1 as a flow-direction center line. Small size sheet: P1 and the A2 line with a 100 mm interval in the flow direction relative to the A1 line as the center line in the flow direction, the position in the width direction is random with respect to P1, and the length in the width direction is 200 mm x the length in the flow direction
0mm size small piece sheet: P2 and P3 in the same way
Shows that -10 is sampled.

Then, this small piece sheet (widthwise length 200
(mm x length in the flow direction 50 mm) is placed on a chamber having a smooth surface plate made of sintered metal on the upper surface, vacuum suction is applied to one side of the sheet to adhere to the surface plate, and the roller is attached to the surface plate. A minimum thickness of 0.01 is obtained by running a type thickness gauge (outer diameter 22 mm, width 7 mm) on the surface of the center line: A sheet in the width direction of 150 mm excluding 25 mm at both ends of the small piece sheet.
Continuously measure and record the thickness in mm.

FIG. 5 shows the measured and recorded thickness data curve. The surface smoothness S is divided into one valley to the next valley and that valley to the next mountain. It is the maximum value calculated by the following equation by reading the thickness difference (ΔT: mm) and the span length (L: mm) of the part.

[0031]

## EQU00005 ## S = .DELTA.T / L The surface smoothness (flat S) is the average value of the measured values S at the 10 points where the above operation was repeated.

Explaining the significance of this formula, it is considered that this requirement factor is a numerical representation of the uneven thickness of the foamed sheet, which is one structural index showing how smooth the surface is. There is. For example, a corrugated sheet itself has thickness unevenness in the width direction of the foamed sheet, and the S value shows a large numerical value. That is, since the product having a uniform thickness and a smooth surface is the product of the present invention, it is said that a more desirable surface structure is one in which the S value is small and approximates to 0 (zero).

Table 2 below (corresponding to Example and Comparative Example 1)
Shows the relationship of practical characteristic effects when the S value is used as an index. Here, in order to simplify the relationship of contrast,
The polymer composition used is the same, the apparent density of the target sheet,
Efforts are being made to bring the overall thickness to the same level.

According to the results shown in Table 2, the adhesiveness to the skin material (appearance and adhesive strength), punching workability, thermal vacuum forming performance (wide range of heating conditions), aesthetics (gloss and surface of the foamed sheet). From the viewpoint of ensuring that all of the (presence or absence of dents) have excellent levels, the meaning that the (plain S) value is at least 0.02 or less has been demonstrated.

The following main requirement of the non-crosslinked foamed sheet of the present invention, namely "the second DSC curve obtained by the differential scanning calorimetry of the non-crosslinked high-foamed sheet", "(1) At least two or more Endothermic peak is (2) 140-16
In the temperature range of 5 ° C., (3) the difference between the temperature at the apex of the low temperature side endothermic peak and the temperature at the apex of the high temperature side endothermic peak is 5
The importance of the requirement portion that is “° C. or higher” is to exert the effect of improving the deep drawing formability and heat resistance. This requirement is that the above-mentioned surface smoothness (flat S) is satisfied, and a wide range of molding heating conditions is satisfied, and the relationship there is shown in Table 3.

First, the meaning of the second DSC curve obtained by differential scanning calorimetry will be explained. It is considered that this requirement factor is one of the polymer structural characteristics that the present inventors have clarified. Figure 3 is a typical second D
In the figure, the curve I represents the non-crosslinked highly foamed sheet of the present invention (foamed sheet obtained by the method of the present invention in Experiment No. 1), and the curve II represents the non-crosslinked product of the comparative product. Highly foamed sheet (random copolymerized propylene resin foamed sheet obtained in Experiment No. 15) and the curve III in the figure shows the non-crosslinked highly expanded sheet of the comparative product (block copolymerized propylene resin foamed sheet obtained in Experiment No. 19). ) The second D obtained by measuring
It is an SC curve result.

As a result of repeated studies on the thermoforming performance of the non-crosslinked high-foam sheet of interest, the present inventors have found that the above DS
We noticed that the C-melting characteristics greatly depended on the thermoformability, and made the final decision. That is, in the case of melting behavior in a narrow temperature range like III in FIG. 3, the moldable temperature is only a point and industrial molding is impossible, and like II in FIG. In the case of a material having a wide temperature range and exhibiting a gentle melting behavior, the temperature range in which molding is possible can be taken, but the temperature dependence of viscoelasticity is still large and deep drawing cannot be carried out.

From these phenomena, focusing on the appearance of DSC melting characteristics of an uncrosslinked high-foaming sheet exhibiting excellent deep-drawing moldability, various propylene-based resins and their mixed combination resins were subjected to foaming trial production and DSC measurement. And the thermoformability evaluation was repeated and completed. The requirement factor is that the difference between the temperature at the apex of (1) at least two or more endothermic peaks and (3) the apex of the low temperature side endothermic peak and the apex of the high temperature side endothermic peak is 5 ° C. or more. As a typical DSC curve of the present invention, the I curve (two endothermic peak temperatures (151 ° C., 160 ° C.) and ΔT in FIG.
(9 ° C.)) is presented.

Here, the second DSC curve, that is, "3 to 5 mg of the foamed sheet was measured at 20 ° C. from room temperature by a differential scanning calorimeter.
The curve obtained when the temperature was raised to 0 ° C. at a rate of 10 ° C./min was used as the first DSC curve, and then the temperature was lowered from 200 ° C. to 40 ° C. at a rate of 5 ° C./min, and again 10 ° C./min.
The reason why the "curve obtained when the temperature is raised to 200 ° C. at a heating rate of 1 minute" is adopted will be explained.
The heat treatment effect during foaming (heating temperature rising rate, foaming temperature, cooling rate) is not absent in the SC curve, and this is because it has a difference in melting characteristics in the thickness direction of the foamed sheet, so it is rather thermoforming. There was a problem that data could not be grasped because it could not be correlated with performance. As will be described later, there is a correlation between the deep-drawing thermoforming performance and the second DSC curve characteristic, and therefore the second DSC curve showing the true melting characteristic is adopted.

Table 3 (corresponding to Example and Comparative Example 2) shows the relationship between the second DSC curve of the non-crosslinked highly foamed sheet, that is, the effect of improving the thermoforming performance and the heat resistance viewed from the polymer melting property as an index. Is shown. Here, in order to simplify the relationship of comparison, efforts are made to make the surface smoothness (flat S), apparent density, and overall thickness of the target sheet uniform.

According to the results shown in Table 3, from the viewpoint of adding the deep drawability required for complicated thermal vacuum forming of automobile molding ceiling materials, etc., it was obtained by differential scanning calorimetry of an uncrosslinked high foam sheet. In the second DSC curve obtained, it is meant that at least two or more endothermic peaks and the difference between the temperature at the apex of the low temperature side endothermic peak and the temperature at the apex of the high temperature side endothermic peak is 5 ° C. or more. Has been proven.
From the viewpoint of having both heat-resistant dimensional stability, it has been proved that the endothermic peak is in the temperature range of 140 to 165 ° C.

The cell diameter of the non-crosslinked high-foam sheet according to the present invention is not particularly limited, but it is preferably 2 mm or less, more preferably 0.5 mm or less in order to ensure heat insulation and cosmetic properties.

Next, a method for producing the non-crosslinked highly foamed sheet of the present invention will be described. The main points of the manufacturing method of the present invention are:
(A) Carbon number of 2 to 20 having an endothermic peak at 135 to 150 ° C. by differential scanning calorimetry (heating rate 10 ° C./min)
Random copolymerized polypropylene resin (A) with α-olefin of 55 to 95% by weight, a polypropylene homopolymer having an endothermic peak higher than that of the random copolymer by 10 ° C. or more, a block copolymerized polypropylene resin with ethylene,
One or more combination resins (B) among random copolymer polypropylene resins with α-olefins having 2 to 20 carbon atoms
Using a mixed resin consisting of 5 to 45% by weight,
(B) The resin of (a) above is melted and kneaded through an extruder and extrusion-molded into a sheet, and the elemental sheet is impregnated with a volatile foaming agent or an inorganic gas, (c) and the resin (B).
The foaming rate is 0.2 to 1.0 times / second with steam having a temperature lower than the melting point.

First, the necessity of the above-mentioned main point (a) is that at least two or more endothermic peaks of 140 to 165 are included in the second DSC curve obtained by the differential scanning calorimetry of the above-mentioned non-crosslinked highly foamed sheet. In the temperature range of ℃, the cross-linked high-foaming sheet of the present invention having a main part having a difference of 5 ° C. or more between the temperature at the apex of the low temperature side endothermic peak and the temperature at the apex of the high temperature side endothermic peak. To make it appear. The relationship between these places is shown in Table 3.

According to Table 3 (corresponding to Example and Comparative Example 2), at least two endothermic peaks are shown, and the temperature at the apex of the low temperature side endothermic peak and the temperature at the apex of the high temperature side endothermic peak are shown. In order to develop a non-crosslinked highly foamed sheet having a difference of 5 ° C. or more, Experiment No. 8 (Endothermic peak 13 of resin A
Mixing 8 ° C. and 148 ° C. of endothermic peak of resin B, temperature difference 10 ° C.) and Experiment No. 20 (Endothermic peak 14 of resin A above 14
In comparison with the result of the mixture of 0 ° C. and the endothermic peak of 148 ° C. of the B resin, a temperature difference of 8 ° C.), it means that the endothermic peak temperature of the B resin is higher than the endothermic peak temperature of the A resin by 10 ° C. or more. The resin B has been proved to have a higher endothermic peak than that of the resin A by 10 ° C. (a polypropylene homopolymer, a block copolymer polypropylene resin with ethylene, an α-olefin having 2 to 20 carbon atoms). Experiment No. 1, one or more combination resins of random copolymer polypropylene resin of No. 1) may be used. 8 ~
The results of No. 14 are verified, and further, the experiment No. 1, 6,
7, 15, 16, 17, 18, 19 (Endothermic peak 140
From the results of experiments in which the mixing ratio was changed using two kinds of resins having a temperature difference of 23 ° C. between the A resin of C and the B resin having an endothermic peak of 163 ° C., the A resin of 55 to 95% by weight and the The significance of using a mixed resin consisting of 5-45 wt% B resin has been demonstrated. On the contrary, this result indicates that the mixed resins used in the present invention do not show the unique endothermic peaks when they are used alone, but they have a unique crystal morphology that changes depending on the mixing ratio by forming mixed crystals by mutual melting and compatibilization. Suggests to take.

Further, according to Table 3 (corresponding to Example and Comparative Example 2), in order to develop a non-crosslinked highly foamed sheet having two or more endothermic peaks in the temperature range of 140 to 165 ° C., an experiment was conducted.
No. 11 (mixture of the endothermic peak 137 ° C. of the A resin and the endothermic peak 163 ° C. of the B resin) and Experiment No. 11 21 (a mixture of the endothermic peak 131 ° C. of the A resin and the endothermic peak 163 ° C. of the B resin), and both of them were in a strict mixing ratio of 90% by weight of the random copolymerized polypropylene resin (A resin), The significance of using a random copolymerized polypropylene resin having an endothermic peak above 135 ° C has been demonstrated.

Further, the necessity of the above-mentioned main point (a) is to obtain a non-crosslinked highly foamed sheet having a high closed cell rate (90% or more). The relationship between these is shown in Table 4.

Table 4 (corresponding to Example and Comparative Example 3) shows that "air is additionally added into the bubbles of the non-crosslinked foamed sheet, which will be described later, and heating is performed in a state where the pressure inside the bubbles is high to achieve high foaming. Method ”. For details, see Experiment Nos. Of Examples and Comparative Example 2. 1,6,7,16,17,18 using the non-crosslinked foamed sheet having an apparent density of 0.060 g / cm ^{3 and} adding each of them with air so that the foaming ratio becomes about 1.8 times. After adjusting the amount, heat foaming, apparent density 0.033
This is an evaluation to obtain a non-crosslinked foamed sheet of g / cm ³ .

The results shown in Table 4 indicate that resin compositions deviating from the above-mentioned main point (a) (corresponding to Experiment Nos. 2, 5, 28, and 27) did not cause high foaming up to the target apparent density. Moreover, it is shown that the closed cell ratio does not reach the target level (90% or more) and only a foamed sheet having poor compression recovery is obtained. That is, in order to obtain a non-crosslinked highly foamed sheet having a high closed cell rate (90% or more), the resin composition (resin mixing ratio: A / B = 95 /
5 to 55/45) is required.
Furthermore, the experiment No. of Table 5 (corresponding to the example and the comparative example 4). Two
9, the apparent density of 0.
It has been demonstrated that an uncrosslinked, highly foamed sheet of 020 g / cm ³ is obtained.

To summarize the above results, the use of the resin composition having the above-mentioned main point (a) is effective in improving the deep drawing formability of the above-mentioned non-crosslinked high-foamed sheet, and the "surface-smooth non-crosslinked high-expansion sheet" described later. This means that the composition is optimal for the above-mentioned main points (b) and (c) of the method of producing a foamed sheet, and high foamability is exhibited.

For example, the method of obtaining a non-crosslinked highly foamed sheet by the extrusion foaming method described in the above-mentioned JP-A-62-192430 (however, the thermoformability is not described) is the temperature-dependent foaming from the melt state by temperature change. Since the viscoelastic behavior is different from the temperature-rise heating from room temperature to immediately before crystal melting in thermoforming, the resin composition does not satisfy high foamability and deep drawing thermoformability. On the other hand, the above-mentioned main point (b), which will be described later,
Since the foaming method of the present invention of (c) is the same heating and heating as in the case of thermoforming, a resin composition satisfying both high foaming property and deep drawing thermoformability, that is, the above-mentioned main point (a) It is assumed that the resin composition can be selected.

As a random copolymer polypropylene resin (A) with an α-olefin having 2 to 20 carbon atoms, which has an endothermic peak at 135 to 150 ° C. by differential scanning calorimetry (heating rate 10 ° C./min) used in the present invention. Are well known as ethylene-propylene random copolymers or ethylene-propylene-butene random copolymers. The content of the α-olefin having 2 to 20 carbon atoms has an endothermic peak of 13
It may be in the range of 5 to 150 ° C. and is not particularly specified. The MFR may be 40 g / 10 min or less, but from the viewpoint of foaming performance, the range of 0.3 to 15 g / 10 min is preferable.

Further, polypropylene homopolymer, block copolymer polypropylene resin with ethylene, carbon number 2 to
As one or more combination resins (B) among 20 random copolymer polypropylene resins with α-olefins,
A resin having an endothermic peak higher than that of the random copolymer (A) by 10 ° C. or more may be used. From the perspective of foaming performance, MFR1
It is preferably 0 g / 10 minutes or less.

It is preferable that the MFR of the (A) resin and the MFR of the (S) resin are similar to each other or that the MFR of the (A) resin has a higher value. On the other hand, other resins such as polystyrene resin, low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-medium-density polyethylene and the like are mixed with a proportion of 20% or less with the above polypropylene resin. It may be a composition. Next, the main points (b) and (c), which are the foaming methods of the resin composition of the above-mentioned main point (a), will be described.

First, the necessity of the main points (b) and (c) is divided, for example, from the known extrusion foaming method (described in JP-A-58-49730 and JP-A-62-192430). This is a novel method for foaming a non-crosslinked polypropylene resin sheet, which produces excellent characteristics not found in non-crosslinked highly foamed sheets. That is, since the above-mentioned extrusion foaming method is the temperature-decreasing foaming from the melt state due to the temperature change before and after the foaming, the resin (A) having a lower endothermic peak temperature (melting point) than the resin (B) is the main component. It is unsuitable for high foaming in a certain mixed resin composition of the present invention, for example, a non-crosslinked high foam sheet having a high closed cell ratio is obtained by the resin composition of the above-mentioned main point (a) excellent in deep drawing thermoformability. When trying to obtain, it is necessary to have a foaming temperature condition below the melting point. On the contrary, this foaming condition is unstable foaming such as crystallizing in the die and has flexibility without surface cracking. I cannot make a quality foam sheet.

The foaming agent is homogeneously mixed in a high temperature and high pressure state, cooled to near the melting point, and extruded into the atmosphere from a die attached to the tip of the extruder to make high foaming instantaneously by utilizing the pressure difference. There is a problem that it is extremely difficult to carry out foam molding, and as a result, it is not possible to obtain a sheet having a smooth surface and good cosmetic properties such as the non-crosslinked high foam sheet of the present invention.

On the other hand, the main points (b) and (c) of the foaming method of the present invention are optimum for the foaming method of the resin composition (a) above since they are foaming by heating at elevated temperature. There is an advantage that the speed can be easily controlled. The meaning of this foaming speed control is the control of the strain change speed of foaming, and the strain change speed is adjusted to a speed at which the restraining force of the unfoamed portion acting as a reaction against it can be sufficiently relaxed,
This is to form a foamed sheet with a smooth surface.

The foaming behavior in this case depends on the gel viscosity (depending on the polymer used and the type and amount of the foaming agent contained) and the foaming agent gas pressure (depending on the type and content of the foaming agent) during heat foaming. Depending on the magnitude of the force difference, and the heating conditions related to these (steam pressure rising speed, pressure holding time,
Step-down speed). It is difficult to express these values numerically, and in short, it is necessary to set the above-mentioned adjustment conditions with the foaming rate of 0.02 to 1.0 times / second as an index.

According to the example and the comparative example 1, under the foaming condition that the foaming rate is less than 0.2 times / sec, the diffusion of the foaming agent which does not contribute to the foaming from the sheet into the external atmosphere during the temperature-rise heating foaming. As a result, the foaming efficiency decreases, and a foamed sheet having a target magnification cannot be obtained, or the foamed sheet has uneven foaming. On the other hand, under the foaming condition in which the foaming rate exceeds 1.0 times / second, the surface smoothness (flat S ) A foamed sheet having a value exceeding 0.02 is obtained.

Judging from the result of the above phenomenon, the foaming rate was set to 0.
It is preferable to control foaming at 2 to 1.0 times / second,
Moreover, it turns out that it is an essential requirement. The ultimate expansion ratio is
It depends on the foaming agent content and heating conditions (steam pressurization rate, holding pressure and its time, pressure reduction rate), but the point to keep in mind at this time is not a small foaming temperature (= steam holding pressure) but the melting point of the resin (B). To set a lower temperature. This necessity is to prevent the resin from flowing and to obtain a non-crosslinked highly foamed sheet having a good closed cell structure as shown in FIG.

Another point to be noted is that when the mixed resin is extruded into a sheet through an extruder, the resin (A),
(B) is to be sufficiently melt-kneaded so that the microdispersion is in a uniform compatible state, and the sheet is formed in a slowly cooled state. This need is to keep the polymer structure of the blowing agent-impregnated foam sheet as homogeneous as possible. When impregnating the elemental sheet with a volatile foaming agent or an inorganic gas,
The impregnation temperature is not a little lower than the heat distortion temperature of the resin (A). This need is to prevent sticking and deformation of the sheet.

In the above-described production method of the present invention, when the mixed resin is extruded into a sheet shape by passing through an extruder,
It is also possible to employ a sheet having a foaming ratio of 1.5 times or less, which is obtained by supplying a chemical foaming agent together with a resin and performing extrusion microfoaming. Further, it is also possible to adopt a multi-step sequential foaming method in which the elemental sheet is impregnated with a volatile foaming agent or an inorganic gas and foamed to obtain a highly foamed sheet, in which the inorganic gas is further added to heat and foam. is there.

As the volatile foaming agent or inorganic gas used in the present invention, a usual volatile foaming agent or inorganic gas used for foaming polypropylene resin can be used. Aliphatic hydrocarbons such as propane, butane, pentane; 1,1,1,2-tetrafluoroethane (F
-134a), 1,1-difluoroethane (F-152
a), 1,1,2,2,2-pentafluoroethane (F
-125) and the like, volatile foaming agents of fluorinated hydrocarbons having an ozone depletion potential ODP = 0, and inorganic gases such as nitrogen, air and carbon dioxide. Among them, F-134a, which has a low gas permeation rate and is a nonflammable gas, is a particularly preferable foaming agent.

Based on the above-mentioned production method of the present invention, the adhesiveness with the skin material, the punching workability, the aesthetic property, the thermal vacuum forming performance, which the conventional non-crosslinked high-foaming sheet does not have, are available.
Excellent heat insulation performance and flexibility (Experiment No.
1, 22 and 32, 33)), "in the second DSC curve obtained by differential scanning calorimetry, at least two or more endothermic peaks are shown in the temperature range of 140 to 165 ° C. The difference between the temperature at the apex of the low temperature side endothermic peak and the temperature at the apex of the high temperature side endothermic peak is 5 ° C. or more,
In addition, the non-crosslinked polypropylene resin highly foamed sheet of the present invention having a surface smoothness (flat S) of 0.02 or less "can be produced.

Further, the non-crosslinked polypropylene resin highly foamed sheet of the present invention can be said to be an extremely superior sheet which is rich in usefulness because it can be a substitute sheet for the crosslinked highly foamed sheet having a waste problem. And this manufacturing method,
We have achieved high foaming of non-crosslinked polypropylene resin sheet, which has a smooth surface and beautiful appearance, which was previously impossible to achieve, and contributes to resource saving and energy saving by omitting the crosslinking step. , Its technical significance is extremely high.

Evaluation Method: 1) Apparent Density (g / cc) Accurately cut from a test piece into a size of 10 × 10 cm square,
It is a value obtained by measuring the weight and thickness and dividing the weight by the volume, and expressing the weight per unit volume. 2) Closed cell ratio (%) It is a value measured by the air pycnometer method (manufactured by Beckman, model 930) described in ASTM-D2856. (Average of n = 5) Evaluation scale

[0067]

[Table 1]

3) Compression recovery property According to JIS K 6767, compression set CS (%)
And repeated compression set RCS (%) was measured, and (C
It is evaluated by the product value of (S) × (RCS). Evaluation scale

[0069]

[Table 2]

4) Average thickness (mm) It is an average value measured with a digital caliper at intervals of about 20 mm in the width direction of the test piece.

5) Adhesion state with skin material A thermoplastic olefin elastomer (Mitsui Petrochemical Co., Ltd., Mirastomer 5030N) 0.3 mmt sheet skin material was placed on one surface of the test piece, and a heating roll at 200 ° C. was applied from this skin material surface. The resulting laminated product was subjected to the following evaluation by thermocompression bonding (2 mmt compression) and heat bonding. Surface condition at room temperature Visually check the surface condition of the laminated sheet with an area of 2m ²
It is evaluated by the presence or absence of band-shaped streaks of 50 mm and wrinkles. Evaluation scale

[0072]

[Table 3]

Surface Condition at High Temperature This evaluation is to visually evaluate the surface roughness of the laminated sheet surface caused by heating.
The change before and after heating with hot air for 1 minute (peeling, blister) is shown. Evaluation scale

[0074]

[Table 4]

6) Punching Workability (Dimensional Accuracy) Test pieces were stacked in a thickness of about 40 mm, the blade height was 7 mm and the blade thickness was 1.
Place the uppermost sheet surface on a circular press blade with a diameter of 2 mm and a diameter of 15 mmφ so that the top surface of the sheet comes into contact with each other and is instantly compressed by 85% with a hydraulic press machine. Evaluate that the accuracy is good. Evaluation scale

[0076]

[Table 5]

7) Cosmeticity Surface dents Both the front and back sides of a 1 m ² sheet are visually inspected, and the number of dents (mortar-shaped recesses having an outer diameter of about 3 to 10 mm) formed therein are counted and evaluated. Evaluation scale

[0078]

[Table 6]

Surface glossiness The surface of the skin of the test piece was manufactured by Nippon Denki Kogyo, Gloss M
Ecer VC-10 type is mounted, the irradiation angle is adjusted to 45 °, and the reflectance is measured and evaluated according to the following criteria. Evaluation scale

[0080]

[Table 7]

8) Thermal vacuum forming performance Heating condition width: 5.4 kW in an area of 250 mm × 250 mm at intervals of 20 cm above and below
Using the vacuum forming machine (manufactured by Erich Co., Ltd.) equipped with the In France tine heaters on both the upper and lower sides, the vertical opening 1
50mm, width 80mm, bottom length 120mm, width 60mm, depth 30mm square mold is formed, and on the premise that it is a molded product of quality with no wrinkles, uneven thickness, or surface roughness. Evaluation is made based on the length of heating time during which each test piece can be molded. Evaluation scale

[0082]

[Table 8]

Deep drawability Using the vacuum forming machine described above, a die having a 150 mm square opening, a draft of 6 °, and a bottom corner R2.5 of which the depth can be arbitrarily adjusted can be used to form a draw ratio. Was evaluated. The aperture ratio is given by the following equation.

[0084]

[Equation 6] Q-H / W Q: Drawing ratio H: Depth of molded product (mm) W: Opening length of molded product 100 mm Judgment of quality is made by molding without any cracks or surface roughness on the molded product surface. And the ratio (a / b) of the inner dimension (a) of the recess of the molding die to the outer dimension (b) of the molded product is 0.
The case of 95 or more was defined as the moldable range. Evaluation scale

[0085]

[Table 9]

9) Heat resistance In accordance with the measuring method specified in JIS-K-6767, the heat shrinkage rate in each of the vertical, horizontal and thickness directions by heat treatment is shown. Specifically, vertically on the test piece for measurement,
After making a square mark of 10 cm on each side and measuring the thickness,
Heat treatment is performed in a hot air oven at 120 ° C. for 22 hours. After cooling to room temperature, the length, width, and thickness dimensions are measured, and the following evaluation is performed based on the magnitude of the dimensional change (heat shrinkage rate) due to this heat treatment. Evaluation scale

[0087]

[Table 10]

10) Comprehensive Evaluation The following scales are evaluated as a comprehensive evaluation result. Evaluation scale

[0089]

[Table 11]

11) Adiabatic performance (thermal conductivity) In accordance with ASTM-C-518, kcal / m. hr. It is evaluated in the unit of ° C and the value of 0 ° C. Evaluation scale

[0091]

[Table 12]

12) Visual observation of the surface condition after bending the flexible test piece by 180 °
It is evaluated by the presence or absence of surface cracks. Evaluation scale

[0093]

[Table 13]

13) Adaptation Test as Molded Ceiling Base Material Thermoplastic olefin elastomer (Mitsui Petrochemical Co., Ltd., Mirastomer 5030N) 0.3 mmt sheet skin material was thermocompression bonded (2 mmt compression) to one side of the foamed sheet and heat-bonded. The following evaluation was performed using the obtained laminated product.

Practical heat resistance The laminated sheet (length: 500 mm, width: 50 mm) with the foamed sheet facing upward is placed on a supporting frame having a span length of 400 mm, and 1
After heating for 24 hours in a hot-air circulating thermostat maintained at 20 ° C ± 1 ° C and allowing to cool at room temperature, the amount of sagging Lmm of the center of the test piece Lmm
Is measured, and the sagging rate = (L / 400) × 100 is calculated. Evaluation scale

[0096]

[Table 14]

Thermoformability Using a large vacuum forming machine having a wide one-shot forming area,
It has a corner curvature of 60R with an opening of 800 mm in length and 600 mm in width, and a flat shape with a complex shape of 80 mm in depth having a convex part with a diameter of 50 mm and a height of 40 mm in the center, so that a foamed sheet appears on the convex surface of the molded product. Then, the surface condition (wrinkles, surface roughness) of the molded product is visually evaluated. Evaluation scale

[0098]

[Table 15]

14) Repelletability After crushing the test piece, a vented extruder (40 mmφ, L / D)
= 32), melted and degassed, continuously extruded in a strand form (about 2 mmφ) from a die, cooled with water and passed through a pelletizer to obtain pellets. At this time, it was evaluated whether or not the strand could be pulled stably. Evaluation scale

[0100]

[Table 16]

[0101]

EXAMPLES The contents of the present invention will be described in detail below with reference to examples. Example 1 and Comparative Example 1 This experiment is for showing the significance of viewing the structural index referred to in the present invention, that is, the surface smoothness S exhibited by the non-crosslinked high-foamed sheet, as a sheet quality and a management index during secondary processing. It is a thing. In other words, it is a proof of the fact that the sheet quality and the secondary processing performance cannot be exhibited unless the structural index and the surface smoothness S obtained under the method conditions of the present invention are satisfied.

A mixture of 75% by weight of an ethylene-propylene-butene random copolymer (resin A in Table 1) and 25% by weight of an ethylene-propylene block copolymer (resin F in Table 1) was biaxially extruded with a diameter of 65 mm. Melt kneading with a machine, extruding from a coat hanger type T die connected to this extruder, and then passing through a polishing roll to obtain a foaming agent-impregnated foaming sheet having a smooth surface of 1.2 mmt.

This long sheet was placed in a pressure resistant container, and 1,1,1,2-tetrafluoroethane (F-18
4a) liquid is injected, pressure 28.4 kg / cm ² G, temperature 85
F-134a in the raw sheet for 2 hours under the condition of
Was impregnated. Then, after cooling the inside of the container to room temperature, it was taken out from the inside of the container into the atmosphere, and the amount of impregnated F-134a at 1 minute and 30 minutes after taking out was measured, and it was found that no gas escaped. there were.

Immediately after the impregnation, the continuous foamable resin sheet was immediately expanded into a continuous foaming device (steam rising / lowering in the sheet running direction).
Supply to a heating tunnel capable of controlling the pressure reduction, preheating zone; steam pressure 2.0 kg / cm ² G (137 ° C.), sheet running dwell time 5 seconds, heating heating foaming start zone; steam pressure 2.0 kg / cm ² G (137 ° C) to 3.4 kg / cm
Almost linear gradient pressure at ² G (147 ° C), seat running stagnant time 22 seconds (steam heating pressurization rate 0.064 kg /
cm ² G ・ sec), foaming zone; steam pressure 3.4 kg / cm
² G (147 ° C), sheet running dwell time 18 seconds, cooling / cooling zone; steam pressure 3.4 kg / cm ² G (147
℃) to 0.2 kg / cm ² G (105 ℃) with a substantially linear gradient pressure and heating conditions such that the sheet running stagnant time is 5 seconds to continuously foam, and an apparent density of 0.060 g / cc (foaming ratio) 15.2 times), closed cell rate 99%, average thickness 3.0 mm
A highly foamed sheet of

The change behavior of the foaming ratio with respect to the heating time until the formation of this highly foamed sheet was examined. The exit point of the preheating zone = foaming ratio of 1.0 times (non-foaming), the exit point of the temperature rising heating foaming initiation zone. = Expansion ratio 4.4 times, foaming zone exit point = foaming ratio 15.0 times, cooling / cooling zone exit point = foaming ratio 15.2 times (final foaming ratio), and the maximum foaming rate is 0. 2 times / second (= 4.4 times /
22 seconds). This is Experiment No. Set to 1.

FIG. 1 shows a conceptual drawing of a local image obtained by enlarging the cross section in the width direction of the non-crosslinked highly foamed sheet obtained in this experiment.
From FIG. 1, it can be clearly seen that the foamed sheet of the present invention has uniform cell diameters in the width direction and has a relatively smooth surface state.

Temperature rising heating foaming start zone (steam pressure 2.0 kg / cm ² G (137 ° C.) to 3.4 kg / cm ² G
(Slope pressure linear to 147 ℃) sheet running dwell time for 8 seconds (steam heating pressurization rate 0.175 kg / cm ² G
・ Second), 4 seconds (steam heating boost rate 0.35kg / cm
² G ・ sec), 2 sec (steam heating boost rate 0.70 kg
/ Cm ² G · second), 1 second (steam heating pressure rising speed 1.4)
0 kg / cm ² G · sec) except for the purpose of simplifying the comparison, other process conditions are the same as those in Experiment No. The experiment was repeated in the same manner as in No. 1, but with an effort to align the apparent density (g / cc) and the average thickness (mm). The expansion ratio at the exit point of the temperature rising and heating foaming initiation zone, which is the change condition point, is about 4.0 times, 4.0 times, 3.0 times, 2.0 times, and the maximum foaming rate is 0.5. Times / second, 1.0 times /
Seconds, 1.5 times / second, and 2.0 times / second. Experiment this
No. The serial numbers 2, 3, 4, and 5 are attached.

The obtained experiment No. The results of measuring the surface smoothness S of the foamed sheets 1 to 5 by the method described in the text are shown in Table 2. According to this result, the foaming rate is 1.0
Under the foaming condition of more than twice / second, the surface smoothness (flat S) value exceeds 0.02 because the restraining force of the unfoamed portion acting as a reaction to the strain change speed is not sufficiently relaxed. You can see that it will be a sheet.

Further, the temperature rising heating foaming start zone (steam pressure 2.0 kg / cm ² G (137 ° C.) to 3.4 kg / cm ²
G (147 ° C) linear gradient pressure) The sheet running dwell time is 30 seconds (steam heating pressurization rate 0.047 kg / cm
Experiment No. ² except changing to ² G ・ sec) The experiment was conducted under the same conditions as in 1. The expansion ratio at the exit point of the temperature rising and heating foaming start zone, which is a change condition point, is 4.6 times, and the exit point of the cooling and cooling zone = expansion ratio of 12.0 times (final expansion ratio), The maximum foaming rate was 0.15 times / second (= 4.6 times / 30 seconds). The foamed sheet obtained had an inferior appearance with depressions on the surface.

From this result, under the foaming condition that the foaming rate is less than 0.2 times / sec, the foaming agent that does not contribute to foaming increases from the sheet to the external atmosphere during the temperature-rising heating foaming, and thus foaming occurs. It is understood that the efficiency is lowered, a foamed sheet having a target magnification cannot be obtained, or the foamed sheet has uneven foaming, which is not preferable. From the results of the above phenomena, it is understood that it is preferable to control the foaming at a foaming rate of 0.2 to 1.0 times / second, and it is an essential requirement.

The above experiment No. For the foamed sheets 1 to 5, the state of adhesion to the skin material (appearance and adhesive strength), punching workability, thermal vacuum forming performance (wide range of heating conditions), and aesthetics (of the surface of the foamed sheet) by the methods described in the text The gloss and the presence / absence of dents were evaluated and are shown in Table 2 together with the index S indicating the surface smoothness. According to Table 2, if the (flat S) value is at least 0.02 or less, adhesion with the skin material, secondary workability such as wide range of heating conditions during punching and thermal vacuum forming, and surface depression It can be seen that a high-quality non-crosslinked high-foaming sheet that satisfies all the aesthetic requirements of being glossy without being obtained.

Example 2 and Comparative Example 2 This experiment shows the significance of seeing the polymer structural characteristics referred to in the present invention, that is, the crystal melting characteristics of the non-crosslinked high-foamed sheet, as a control index of thermal vacuum moldability and heat resistance. It is for the purpose of showing. In other words, the fact that the deep drawability during hot vacuum forming cannot be exhibited unless the melting characteristics of the non-crosslinked high-foam sheet obtained by the polymer composition and process conditions of the present invention are satisfied is demonstrated. is there.

Therefore, the sheets used in the experiment were made so that the apparent density (0.060 g / cc) and the average thickness (3.0 mm) were all at the same level.
Experiment No. The non-crosslinked highly foamed sheet obtained by using the same process and apparatus conditions as in No. 1 is provided, and the comparison relationship is easily understood.

That is, except that the resins shown in Table 1 were mixed so as to have the composition ratios shown in Table 3, the above experiment was conducted.
No. Repeated using the conditions of 1 experimental method (maximum foaming rate 0.2 times / second (= 4.4 times / 22 seconds) and foaming conditions at a temperature lower than the melting point of the resin (B)). It is an experiment. Experiment No. The serial numbers from 6 to 21 are assigned.

Surface smoothness of obtained foamed sheet (flat S)
Was evaluated by the method described in the text, and Experiment No. 1 of Example 1 and Comparative Example 1 were evaluated. A value similar to the case of 1, 0.005 to 0.
No. 007, and the experiment No. It was shown that the foamed sheets of 6 to 21 were all high quality sheets that could be subjected to molding processing.
Therefore, it was decided to measure and evaluate the second DSC curve of each of these non-crosslinked highly foamed sheets by the method described in the text. The results of this treatment are shown in Table 3.

According to the results shown in Table 3, there are at least two endothermic peaks, and the difference between the temperature at the apex of the low temperature side endothermic peak and the temperature at the apex of the high temperature side endothermic peak is 5 ° C. or more. In order to develop a crosslinked high-foam sheet, Experiment No.
8 (in the case of the endothermic peak 138 ° C. of the A resin and the endothermic peak 148 ° C. of the B resin, a temperature difference of 10 ° C.) and Experiment No. Two
0 (mixing of the endothermic peak 140 ° C. of the A resin and 148 ° C. of the B resin, temperature difference 8 ° C.), the endothermic peak temperature of the B resin is compared with the endothermic peak temperature of the A resin. The meaning of being higher than 10 ° C is proved, and the B resin is a resin having an endothermic peak higher than the endothermic peak temperature of the A resin by 10 ° C or more (a polypropylene homopolymer, a block copolymer polypropylene resin with ethylene,
Experiment No. 1 may use one or more combination resins of (C2-20 random copolymerized polypropylene resin with α-olefin). The results of 8 to 14 have been proved, and further, the experiment No. 1, 6, 7, 15, 16, 17,
18 and 19 (experiments in which the mixing ratio was changed by using two kinds of resins having a temperature difference of 23 ° C. between the A resin having an endothermic peak of 140 ° C. and the B resin having an endothermic peak of 163 ° C.), 55 to 95% by weight and B resin 5 to 45% by weight
It can be seen that the meaning of using the mixed resin consisting of and has been proven.

On the contrary, the results show that the mixed resins used in the present invention do not show the endothermic peaks peculiar to each other alone, but they are mixed and melt compatible to form crystals shared with each other, and are unique to each other depending on the mixing ratio. It suggests that it takes the crystal form of.

Further, according to Table 3, in order to develop a non-crosslinked highly foamed sheet having two or more endothermic peaks in the temperature range of 140 to 165 ° C., Experiment No. 11 (mixture of the endothermic peak 137 ° C. of the A resin and the endothermic peak 163 ° C. of the B resin) and Experiment No. 11 21 (Endothermic peak of resin A above 131 ° C
And the endothermic peak of the above resin B is 163 ° C.), and both are 135 ° C. at a strict mixing ratio of 90% by weight of the random copolymerized polypropylene resin (A resin).
The significance of using the random copolymerized polypropylene resin having the above endothermic peaks has been verified.

Further, Table 3 shows the experiment No. Experiment No. 1 with 6
22 is a table showing a summary of the relationships between the results of deep-drawing molding performance and heat resistance evaluated by the methods described in the text and the indices of the foamed sheets for each of the foamed sheets of Nos. 21 to 21.

According to Table 3, from the viewpoint of adding the deep drawability required for complicated thermal vacuum forming of automobile molding ceiling materials, etc., it can be obtained by differential scanning calorimetry of uncrosslinked high-foamed sheet. In the second DSC curve, at least two or more endothermic peaks, and the difference between the temperature at the apex of the low temperature side endothermic peak and the temperature at the apex of the high temperature side endothermic peak was verified to be 5 ° C. or more. It is understood that the above is performed (relationship between Experiment Nos. 1, 6 to 14 and 21 and Experiment Nos. 15 to 20). From the viewpoint of having both heat-resistant dimensional stability, it has been proved that the endothermic peak is in the temperature range of 140 to 165 ° C (Experiment No.
1, 6 to 20 and the experiment No. 21 relationship).

That is, the results shown in Table 3 are "the second D obtained by the differential scanning calorimetry of the uncrosslinked highly foamed sheet.
SC curve "shows (1) at least two or more endothermic peaks in the temperature range of (2) 140 to 165 ° C. (3) Temperature at the apex of the low temperature side endothermic peak and temperature at the apex of the high temperature side endothermic peak A difference of 5 ° C. or more indicates that the sheet has an excellent effect of improving deep drawability and heat resistance.
It has been proved that it is a requirement for the constitution of the invention that expresses the melting property or viscoelastic property of the sheet.

Example 3, Comparative Example 3 The experiment here is to obtain a foamed sheet having a high closed cell ratio and a high expansion ratio (-low apparent density), which is the object of the polymer composition of the present invention. It means that.

The sheets to be used in the experiment are those of Experiment No. 2 of Example 2 and Comparative Example 2. Using the foamed sheets (apparent density 0.060 g / cc) obtained in 1, 6, 7, 16, 17, and 18,
Air was added and adjusted so that the foaming ratio was 1.8 times in each of the bubbles, and the secondary foaming was performed under the same conditions as the primary foaming performed in each experiment of Example 2 and Comparative Example 2 above. It is foamed.

The obtained foamed sheet was evaluated by the method described in the text, including the index of the foamed sheet (surface smoothness, second DSC curve), adhesiveness with the skin material, punching workability, aesthetics, thermal vacuum forming performance, The heat resistance, the compression recovery property, the apparent density reached and the closed cell ratio were measured and evaluated, and the results are summarized in Table 4.

According to Table 4, in the compositions deviating from the resin composition of the present invention (corresponding to Experiment Nos. 25, 26 and 27), high foaming did not occur up to the target apparent density, and the closed cell ratio was the target. It can be seen that only a foamed sheet which does not reach the level (90% or more) and has poor compression recovery is obtained.
This phenomenon is presumed to be because the temperature range where the composition deviates from the resin composition of the present invention exhibits a large homogeneous elongation is extremely small. In other words, the closed cell ratio is high (90%
In order to obtain the above non-crosslinked highly foamed sheet, the resin composition of the present invention (resin mixing ratio: A / B = 95/5 to 55) is used.
/ 45) confirms the necessity of the constituent requirement.

Example 4 This experiment is to show the applicable range of "apparent density" targeted by the foamed sheet of the present invention. For the purpose of simplifying the application relationship, the foamed sheet here is designed so that the second DSC curve and the index of the surface smoothness S are aligned to a certain level by using one of the resin compositions of the present invention. It is adjusted.

That is, Experiment No. 28 is Example 1 and Comparative Example 1
Experiment No. The F-134a foaming agent impregnation amount was 1.
Experiment No. except that the content was changed to 5% by weight. It is the one completed by repeating the first experiment. Experiment No. No. 29 is the experiment No. 29 of Example 3 and Comparative Example 3. Other than adjusting the additional pressure (amount) of air to 22 so that the foaming ratio becomes 3.0 times,
Experiment No. It was completed by repeating 22 experiments.

The foamed sheet thus obtained was experimentally evaluated in the same manner as in Example 3 and Comparative Example 3, and the index and performance result of the sheet were obtained. It is summarized in Table 5 together with 1, 22.
According to the results in Table 5, the apparent density of the non-crosslinked foamed sheet of the present invention that satisfies the performance of the present invention can be targeted if the apparent density is at least in the range of 0.020 to 0.150 g / cc. I understand.

Example 5 This experiment is intended to show the applicable range of "total thickness" targeted by the foamed sheet of the present invention. For the purpose of making the application relationship simple and clear, the foamed sheet here is prepared by using one composition in the resin composition of the present invention and the apparent density
The SC curve and the index of the surface smoothness S are adjusted so as to be aligned at a constant level.

That is, Experiment No. 30 is Example 1 and Comparative Example 1
Experiment No. In comparison with Experiment 1, the thickness of the foaming agent-impregnated foaming sheet was changed to 0.4 mmt, and the amount of the F-134a foaming agent impregnated was changed to 5.5% by weight. It was completed by repeating the first experiment. Experiment No. 31 is the experiment No. 1, the foaming agent impregnated foaming sheet thickness is 4.0 mmt,
-134a Experiment No. except that the impregnating amount of the blowing agent was changed to 3.5% by weight. It was completed by repeating the first experiment.

The foamed sheet thus obtained was experimentally evaluated in the same manner as in Example 3 and Comparative Example 3, and the index and performance result of the sheet were obtained. It is summarized in Table 6 together with 1. From the results of Table 6, it is understood that the non-crosslinked foamed sheet of the present invention which satisfies the performance of the present invention can be targeted if it has a thickness of at least 1 to 10 mm.

Comparative Example 4 In this experiment, a conventional polypropylene-based resin high-foamed sheet was prototyped using a known manufacturing method, and the performance was evaluated comparatively to show the technical level of the polypropylene-based resin high-foamed sheet of the present invention. Is shown. For the purpose of making the relationship of comparison simpler, the foamed sheet here uses one composition in the resin composition of the present invention, and the index of the second DSC curve and the apparent density, the average thickness, and the closed cell ratio are constant levels. Adjusted to match the values.

<Experiment No. 32, 33 (reference extruded foamed sheet)> The resin shown in Table 1 was blended at the ratio shown in Table 7, and 0.03% by weight of talc was added to the mixture to give 6 mixture.
After melt-kneading at 200 ° C using a 5 mmφ extruder,
Dichlorotetrafluoroethane was pressed into the resin mixture at a ratio of 28 parts by weight with respect to 100 parts by weight of the resin mixture until the end of the extruder was mixed and well mixed. Next, this mixed melt was sent to a second in-line extruder, cooled to 140 ° C. in the second extruder, and extruded and foamed through a 150 mmφ annular die lip. The foam formed was pulled slit on a sizing mandrel and rolled. The obtained foamed sheet had an apparent density of 0.033 g / cc, a thickness of 3 mm, and a closed cell rate of 95%, and was a roll sheet having excellent rolling recoverability. This is Experiment No. It was set to 32.

Experiment No. 1 was repeated except that 14 parts by weight of dichlorotetrafluoroethane was injected under pressure. By the same procedure as 32, a foamed sheet having an apparent density of 0.060 g / cc, a thickness of 3 mm and a closed cell ratio of 96% and having a high compression recovery property was obtained. This is Experiment No. 33. FIG. 2 shows a conceptual drawing of a local image obtained by enlarging the cross section in the width direction of the non-crosslinked highly foamed sheet obtained in this experiment. According to FIG. 2, this extruded foam sheet is randomly arranged such that the cell diameter near the surface in the width direction is a cell group having a small diameter and a cell group having a large diameter, and the surface is wavy and lacks smoothness. You can see that it is in a state.

<Experiment No. 34, 35 (reference article crosslinked foamed sheet)> The resin shown in Table 1 was blended in a ratio shown in Table 7, and 25 parts by weight of an azodicarbonamide foaming agent was added to the mixture to prepare a 65 mmφ twin-screw extruder. It was melt-kneaded at a temperature of 170 ° C. at which azodicarbonamide was not decomposed and then extruded from a coat hanger type T-die connected to this extruder, and then passed through a polishing roll to obtain a surface-active thickness of 0.86 mmt. A sheet for cross-linking and foaming was obtained.

This sheet was irradiated with an electron beam irradiation apparatus (Nisshin High Voltage Co., Ltd., accelerating voltage 750 kV) for 10
Irradiated with a dose of Mrad. The obtained crosslinked sheet is 270 ° C.
It was heated and foamed with a far infrared heater having a surface temperature of.
The crosslinked foamed sheet obtained at this time had an apparent density of 0.03.
It was a crosslinked foamed sheet having a smooth surface with a compression recovery property of 2 g / cc, a thickness of 3 mm and a closed cell ratio of 97%. Experiment this with N
o. 34.

In addition, except that the addition amount of azodicarbonamide was changed to 10 parts by weight and the thickness of the cross-linking and foaming sheet was changed to 1.1 mmt, Experiment No. A crosslinked foamed sheet having an apparent density of 0.060 g / cc, a thickness of 3 mm, and a closed cell ratio of 98% and having a smooth surface and a smooth surface was obtained in the same manner as in Example 34. This is Experiment No. 35.

The above experiment No. The foamed sheets obtained in Nos. 32 to 35 were evaluated in the same manner as in Example and Comparative Example 3 to obtain the index and performance result of the sheet, and the experiment No. 1, 22
In addition, heat insulation performance, flexibility, adaptability as a molded ceiling base material (practical heat resistance and thermoformability), and repelletability were evaluated by the method described in the text, and all of these are shown in Table 7.

According to the results shown in Table 7, the non-crosslinked high-foamed sheet of the present invention is not only excellent in compression recovery and heat resistance, but also has a aesthetic appearance with no dent on the surface appearance and gloss, flexibility and heat insulation. It can be seen that the performance and the secondary processing performance such as adhesiveness with the skin material, punching workability, and thermal vacuum formability are superior to those of the conventionally well-known non-crosslinked extruded highly foamed sheet. Further, it has a feature that thermoforming of a complicated shape is possible, which is not possible with a conventional non-crosslinked extruded highly foamed sheet, and that it can be applied as a molded ceiling base material. Also, since it can be used as a substitute sheet for the crosslinked high-foaming sheet having a waste problem, it can be seen that the sheet is extremely useful and extremely excellent.

[0140]

[Table 17]

[0141]

[Table 18]

[0142]

[Table 19]

[0143]

[Table 20]

[0144]

[Table 21]

[0145]

[Table 22]

[0146]

[Table 23]

[0147]

[Table 24]

[0148]

[Table 25]

[0149]

[Table 26]

[0150]

[Table 27]

[0151]

[Table 28]

[0152]

EFFECTS OF THE INVENTION As described and clarified by using Examples and Comparative Examples, the non-crosslinked high-foam sheet of the present invention has the above-mentioned constitution, thereby improving the cosmetic properties, flexibility and heat insulation performance. It is possible to easily obtain a non-crosslinked polypropylene resin highly foamed sheet which is rich and has excellent secondary processing performance such as adhesiveness with a skin material, punching workability, and thermal vacuum forming property. These properties are comparable to cross-linked high-foam sheets that have a waste problem and meet the wishes of the industry. For example, they are widely used in the insulation of vehicles such as automobiles, cushioning interior materials, and the production of storage containers that can cook food. The product value is extremely high because it can be utilized and useful.

Further, the manufacturing method has achieved high foaming of the non-crosslinked polypropylene-based resin sheet, which has a smooth surface and is beautiful, which has been impossible to realize in the past.
Moreover, the cross-linking step is omitted and it contributes to resource and energy saving, and its technical significance is extremely high. that's all,
It can be said that the present invention is an extremely high and excellent invention that plays a large role in the industrial world.

[Brief description of drawings]

FIG. 1 is a conceptual drawing of a local image obtained by enlarging (× 6 times) a cross section in the width direction of a non-crosslinked highly foamed sheet of the present invention.

FIG. 2 is a conceptual drawing of a local image obtained by enlarging (× 6 times) a cross section in the width direction of a non-crosslinked highly foamed sheet of a comparative product.

FIG. 3 is a graph showing a representative second DSC analysis result.

FIG. 4 is a plan view of a non-crosslinked highly foamed sheet showing measurement points of surface smoothness measurement (flat S).

FIG. 5 is a data diagram obtained by measuring the thickness of a small piece sheet.

[Explanation of symbols]

 I Results of DSC analysis of non-crosslinked high-foamed sheet of the present invention II Results of DSC analysis of non-crosslinked high-foamed sheet of comparative product III Results of DSC analysis of non-crosslinked high-foamed sheet of comparative product

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B29K 105: 04 B29L 7:00 4F C08L 23:10

Claims (2)

[Claims] 1. A non-crosslinked polypropylene resin high foam sheet having a closed cell ratio of 90% or more, an apparent density of 0.020 to 0.15 g / cm ³ , and a thickness of 1 to 10 mm, wherein the foam sheet has a differential scanning calorific value. The second DSC curve obtained by the measurement (however, the curve obtained when the foamed sheet 3 to 5 mg was heated from room temperature to 200 ° C. at a temperature rising rate of 10 ° C./min by the differential scanning calorimeter was used as the first DSC curve. A curve is obtained, and then the curve obtained when the temperature is decreased from 200 ° C. to 40 ° C. at a temperature decrease rate of 5 ° C./min, and the temperature is increased to 200 ° C. at a temperature increase rate of 10 ° C./min is the second DSC curve. ), At least two endothermic peaks
In the temperature range of 0 to 165 ° C., the difference between the temperature at the apex of the low temperature side endothermic peak and the temperature at the apex of the high temperature side endothermic peak is 5 ° C. or more, and the surface smoothness flatness obtained by the following method is A non-crosslinked polypropylene resin highly foamed sheet having a value of S of 0.02 or less. Surface smoothness (flat S)
Is the width-direction length 1 per width-direction total length of the foamed sheet
100 points in the flow direction at one measurement rate over 50 mm
The following measurement was performed at 10 random positions in the width direction at intervals of mm, and the obtained value S is shown as an average value at 10 positions. The measurement is performed by placing a small sheet (200 mm long in the width direction x 50 mm length in the flow direction) on a chamber that has a smooth surface plate made of sintered metal on the top surface, and vacuum suction to bring one side of the sheet into close contact with the surface plate. , A roller (outer diameter 22 mm, width 7 mm) type thickness gauge attached to the surface plate is run in the width direction of 150 mm except 25 mm at both ends of the small piece sheet, and the minimum reading is continuously measured in 0.01 mm units. It was recorded. Then, on this measured and recorded thickness data curve, the peak is divided into the next valley and the valley is divided into the next peak, and the thickness difference (ΔT: mm) between the peak and the valley and the span length ( L: mm) is read and the maximum value calculated by the following formula is adopted. ## EQU1 ## S = .DELTA.T / L This operation is repeated at the above 10 points. 2. A differential scanning calorimetric measurement in a method for producing a non-crosslinked polypropylene resin highly foamed sheet having a closed cell ratio of 90% or more, an apparent density of 0.020 to 0.15 g / cm ³ , and a thickness of 1 to 10 mm. Random copolymerized polypropylene resin (A) 55 to 95% by weight with an α-olefin having 2 to 20 carbon atoms and having an endothermic peak at a temperature rising rate of 10 ° C./min) of 135 to 150 ° C. Polypropylene homopolymer, which is 10 ° C higher than the polymer,
One or more combination resins (B) of block copolymer polypropylene resin with ethylene and random copolymer polypropylene resin with α-olefin having 2 to 20 carbon atoms
45 wt% of a mixed resin is melt-kneaded through an extruder and extruded into a sheet, and the raw sheet is impregnated with a volatile foaming agent or an inorganic gas, and the temperature is lower than the melting point of the resin (B). Non-crosslinked polypropylene resin characterized by having a surface smoothness (flat S) determined by the following method of 0.02 or less by foaming with a steam of 0.2 to 1.0 times / second. Highly foamed sheet manufacturing method. The surface smoothness (flat S) is a measurement ratio at one location over the entire length in the width direction of the foamed sheet, which is 150 mm in the width direction, and the following measurement is performed at 10 locations at 100 mm intervals in the flow direction at random positions in the width direction. It is shown by the average value of the obtained value S at 10 points. The measurement is performed by placing a small sheet (200 mm long in the width direction x 50 mm length in the flow direction) on a chamber that has a smooth surface plate made of sintered metal on the top surface, and vacuum suction to bring one side of the sheet into close contact with the surface plate. , A roller (outer diameter 22 mm, width 7 mm) type thickness gauge attached to the surface plate is run in the width direction of 150 mm except 25 mm at both ends of the small piece sheet, and the minimum reading is continuously measured in 0.01 mm units. It was recorded. Then, on the measured and recorded thickness data curve, the peak is divided into the next valley and the valley is divided into the next peak, and the difference in thickness between the peak and the valley (ΔT:
mm) and its span length (L: mm) are read and the maximum value calculated by the following formula is adopted. ## EQU00002 ## S = .DELTA.T / L This operation is repeated at the above 10 points.