JP2918135B2 - Propylene resin foam sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamed propylene resin sheet.

[0002]

2. Description of the Related Art As a method for producing a long-sized foam or a sheet-like foam for forming a container or the like, a thermoplastic resin is melt-kneaded with a foaming agent in an extruder, and then subjected to low pressure. An extrusion foaming method of extruding and foaming is widely used.

In the extrusion foaming method of an olefin resin, when a melt-kneaded product of a resin and a foaming agent is extruded under a low pressure from an extruder, foaming is performed by expanding the foaming agent in the melt-kneaded material. However, if the temperature of the resin is increased, the viscosity drops sharply, the resin cannot retain the foaming agent, escapes from the resin and becomes a foam of open cells, and conversely, the resin temperature is increased to increase the viscosity of the resin. If the temperature is lowered, crystallization of the resin proceeds, and as a result, the foam does not foam sufficiently and uniformly, and the foam surface becomes uneven. For this reason, extrusion foaming needs to be performed at a temperature at which the resin has sufficient viscoelasticity so that a sufficiently uniform foaming can be performed and a foaming agent can be held in the resin. The temperature range in which viscoelasticity suitable for foaming is obtained differs depending on the type of resin, and this temperature range is generally referred to as a foaming suitable temperature range.

[0004]

However, the propylene-based resin having a higher degree of crystallinity than low-density polyethylene or the like greatly changes the viscoelasticity of the resin due to a slight temperature change, and has a very narrow temperature range for foaming. It is very difficult to carry out extrusion foaming while maintaining the resin temperature within such a narrow temperature range, and when the extrusion foaming temperature fluctuates and deviates from the appropriate foaming temperature range, the foamed portion has an open-cell structure. And the surface became uneven, and it was difficult to obtain a foam having good overall and uniform properties. Conventionally, in the case of a non-crosslinked propylene-based resin, a relatively good foam can be obtained only at a low expansion ratio having a density exceeding 0.2 g / cm ³ or at a density of 0.013 g / cm ^3. It has a high expansion ratio of less than.

[0005] The above-mentioned problems are considered to be caused by the high crystallinity of the propylene-based resin, and the density of the propylene-based resin is not higher than 0.
Extruded foams having a low expansion ratio of more than 2 g / cm ³ can be obtained relatively favorably because the ratio of the resin is larger than the amount of the foaming agent. It is considered that the reason is that the temperature can be set to a considerably higher temperature. The density is 0.013 g / cm ³
The reason why a foam having a high expansion ratio of less than 1 can be obtained relatively favorably is as follows.

In general, a foaming olefin-based resin in the process of extrusion foaming is subjected to a cooling operation from the outside by using a cooling means, whereby the cell wall is solidified to obtain a good foam. However, since the propylene-based resin has a higher degree of crystallinity than low-density polyethylene, the calorific value during crystallization is large. This heat hinders the cooling and thus the solidification of the cell walls, and breaks or deforms the cells of the propylene-based resin in the process of foaming.

Therefore, by foaming a large amount of a foaming agent, the temperature of the propylene-based resin in the course of foaming is rapidly lowered by utilizing the heat of vaporization (heat of expansion) of the foaming agent, thereby solidifying the cell wall. Promote. Further, a large amount of the foaming agent has a function of delaying crystallization of the resin in the extruder. As a result, a relatively good foam can be obtained. However,
In this case, the foam obtained necessarily has a high expansion ratio of less than 0.013 g / cm ³ due to the necessity of blending a large amount of a foaming agent. Also in this case, the suitable foaming temperature range is only about 0.6 ° C.

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, by using a non-crosslinked propylene resin having a long-chain branch and a drawdown property of 60 m / min or less as a base material. The applicant has filed an application for finding that a foamed sheet having a suitable foaming temperature range wider than that of a conventional non-crosslinked propylene-based resin as a base material, and having a uniform and excellent property as a whole can be obtained (Japanese Patent Application No. Hei 10-26139). 3-3550
No. 43).

Although this foamed sheet has an excellent appearance with little shrinkage and corrugation, it has a drawback that the molded article tends to have uneven thickness when subjected to vacuum forming or the like. The thickness unevenness tends to increase as the degree of drawing of the molded product increases. In the case of a sheet in which a non-foamed synthetic resin film is laminated on the surface of a foamed sheet, there is a problem that the laminated film is easily peeled off.

The inventors of the present invention have conducted intensive studies to determine the cause of the unevenness in the thickness of the molded product, and as a result, have confirmed that the cause is the presence of unevenness in the thickness of the foamed sheet.
In addition, even when a specific non-crosslinked propylene-based resin having a long chain branch and a drawdown property of 60 m / min or less is used as a base resin, extrusion foaming can be performed in the same manner as in the related art. It has also been found that it occurs when obtained.

The inventors of the present invention have found that unevenness in the thickness of a molded article using a foamed sheet based on a specific non-crosslinked propylene resin having a long chain branch and a drawdown property of 60 m / min or less is obtained. In order to solve the problem, as a result of further diligent research back to the cause of uneven thickness of the foamed sheet, the thickness of the foamed sheet was reduced by devising foaming conditions when using the specific non-crosslinked propylene resin. A foam sheet having an average minimum thickness / average maximum thickness value of 0.9 or more when measured along the width direction can be obtained. When such a foam sheet is formed, the thickness of the molded article is reduced. They have found that unevenness can be prevented as much as possible, and have completed the present invention.

[0012]

That is, the foamed propylene resin sheet of the present invention has a density of 0.3 based on a non-crosslinked propylene resin having a long chain branch and a drawdown property of 60 m / min or less. ~ 0.06 g / cm ^{3 of} an extruded foam sheet, wherein the value of average minimum thickness / average maximum thickness when the thickness of the foam sheet was measured along the width direction was:
0.9 or more. In the foam sheet of the present invention , the non-crosslinked propylene resin as the base resin is
It is preferable that the drawdown property is 30 m / min or less.
And particularly preferably 15 m / min or less. Also book
The foamed propylene-based resin sheet of the invention is characterized in that
Lamination by laminating non-foamed film on resin foam sheet
It may be of the type.

The base resin constituting the foamed sheet of the present invention must have a long-chain branch in the main chain, unlike ordinary propylene-based resins. This propylene-based resin may be any of a homopolymer, a block copolymer, and a random copolymer.

In the case of a copolymer, a copolymer of propylene and a small amount of an olefin other than propylene is preferred. Examples of the olefin include ethylene and α-olefins having 4 to 10 carbon atoms. Two or more kinds can be used in combination. Examples of the α-olefin having 4 to 10 carbon atoms include 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1-heptene, 3-
Methyl-1-hexene and the like.

The α-olefin is preferably contained in the copolymer in a proportion of usually not more than 20% by weight, particularly preferably not more than 10% by weight. Particularly, when the α-olefin is ethylene, it is preferably not more than 5% by weight. It is preferable that it is contained in a ratio. The preferable lower limit of the content of these α-olefins in the copolymer is 0.5% by weight in the case of any α-olefin.

The propylene-based resin used in the present invention is a normal crystalline linear propylene-based resin (usually a weight-average molecular weight of 100,000 or more) and contains an atactic component and / or an isotactic component. Resins containing non-crystallized components (hereinafter referred to as "normal propylene resins" in order to distinguish them from the propylene resins used in the present invention. Incidentally, when simply referred to as propylene resins, The resin used in the present invention is mixed with a low-temperature decomposition type (decomposition temperature: about room temperature to about 120 ° C.) peroxide and heated to 120 ° C. or less, and atactically attached to the main chain of a normal propylene-based resin. And / or a method in which non-crystallized isotactic components are combined as a branched chain, and usually have a long-chain branch mainly at the end. It believed to have a parting-like structure.

The low-temperature decomposable peroxides include di (s-butyl) peroxydicarbonate and bis (2-
Ethoxy) peroxydicarbonate, dicyclohexylperoxydicarbonate, di-n-propylperoxydicarbonate, di-n-butylperoxydicarbonate, diisopropylperoxydicarbonate,
Examples thereof include t-butyl peroxy neodecanoate, t-amyl peroxy neodecanoate, t-butyl peroxy pivalate, and the like.

The professional resin which is the base resin of the foamed sheet of the present invention
The pyrene-based resin is obtained by stirring the above-mentioned ordinary propylene-based resin.
Such as argon while stirring in a reactor equipped with
Replace the inside of the reaction vessel with gas, and then replace the peroxide with resin
Add usually 5 to 50 mmol per kg and continue stirring
Up to about 120 ° C, preferably about 70 to 105 ° C
To react (usually for 30 to 120 minutes)
After that, the reaction is stopped. In stopping the reaction
Use a reaction stopper such as methyl mercaptan in the reaction vessel
Or the reaction product at 130 to 150 ° C
For example, a method of heating for about 20 to 40 minutes is employed. Step
Whether long-chain branching exists in the propylene-based resin molecular chain
Can be confirmed by the following method. That is, elongational flow
Measuring equipment (eg, rheometrics extensional flow measurement
Apparatus: Propylene-based using RR-9000)
From resinFor prepared measurementsampleof,FixedStrain rate
(Second^-1Elongational viscosity (poise) and time
(Seconds) in a graph. Smell on this graph
Has a long-chain branch and a long-chain branch
The propylene resin that does notFor exampleHas long chain branch
For propylene-based resins, the slope of the elongational viscosity curve increases with time.
BigAnd eventually breaks elasticallyWhereas long
For a propylene-based resin without chain branching, the elongational viscosity curve
It can be distinguished from the fact that the slope decreases over time.
it can. Rheometrics' extension flow measurement device
(ER-9000) shows that long chain branching
-Containing propylene resin and propylene resin having no long-chain branch
Len resinFixedElongational viscosity and time at strain rate
FIG. 5 is a graph showing the relationship. In the graph
Curve A shows a propylene-based resin having a long-chain branch.
Line B indicates a propylene-based resin having no long-chain branch. This
From the graph of, with the propylene resin having a long chain branch
Means that the slope of the elongational viscosity curve increases with time
On the other hand, propylene-based resin without long chain branch
It can be seen that the slope of the viscosity curve decreases with time
You. In addition, measurementforSamples and measurement conditions are as follows
You.・ MeasurementforSample size, shape: length 30mm, diameter
5mm cylinder ・ Strain rate: 1.0 second^-1  ・ Measurement temperature: Melting point of base resin + 20 ° C (However, melting point is based on
1-5 mg of material resin was measured at 10 ° C./min by a differential scanning calorimeter.
Of the endothermic peak of the DSC curve obtained when the temperature is raised in step
Temperature. ) "

The propylene resin which is the base resin of the foamed sheet of the present invention has a drawdown property of 60 m / min or less, preferably 30 m / min or less, particularly preferably 15 m / min or less. The drawdown property means that a molten propylene resin heated to 230 ° C. is extruded into a string at a constant speed of 10 mm / min from a melt indexer nozzle (2.095 mm in diameter, 8 mm in length), and then to the string-like material. After passing through a feed roll located above a tension detection pulley located below the nozzle, the winding speed of the winding roll is gradually increased while winding by a winding roll. And the winding speed of the cord at the time of cutting.

The drawdown property can be adjusted by the number and length of the long chain branches. Generally speaking, this value tends to decrease as the number of long-chain branches increases and the length of the branches increases. Therefore, in order to obtain a desired drawdown copolymer, it is necessary to set reaction conditions in consideration of these factors. In the case where the resin does not have long-chain branching, or has a branching that is too short or slight, or a normal propylene-based resin, the drawdown property exceeds 60 m / min. Extrusion foaming is performed using such a normal propylene-based resin to obtain a foamed sheet having a density of 0.3 to 0.06 g / cm ³ similar to the foamed sheet of the present invention. There are many corrugations and surface irregularities, and the product has no commercial value.

The crystallization time of the propylene resin used in the present invention at the crystallization temperature + 15 ° C. is preferably 800 seconds or more, more preferably 1000 seconds or more. For the measurement of the half-crystallization time, a crystallization rate measuring device can be used.

In order to measure the half-crystallization rate, first, the support holding the film-like sample is put in an air bath of a crystallization rate measuring device to completely melt the sample, and then the molten sample is put together with the support. The sample is immersed in an oil bath maintained at the crystallization temperature of the sample + 15 ° C so as to block the optical path between the light source and the optical sensor, and is always kept at the optical sensor until the melted sample solidifies again. The voltage of the light source is adjusted so that the amount of light is detected, and a voltage-time curve as shown in FIG. 1 is obtained. In this case the voltage when the voltage at the curve becomes a constant value and the V _0, and the time until the voltage becomes 1 / 2V ₀ a half-crystallization time.

In the present invention, not only the above-mentioned propylene resin can be used alone, but also other resins can be mixed and used. As the resin used in combination, for example, a propylene-based resin other than the above, or high-density polyethylene, low-density polyethylene, linear low-density polyethylene,
Ethylene resins such as linear ultra-low density polyethylene, ethylene-butene copolymer, ethylene-maleic anhydride copolymer, butene resins, polyvinyl chloride, vinyl chloride such as vinyl chloride-vinyl acetate copolymer Resins, styrene resins and the like.

When the other resin is mixed, the amount of the resin to be mixed is limited to 40% by weight of the total weight of the polymer after mixing, and the drawdown property of the mixture does not exceed 60 m / min. There is a need.

In the present invention, the above-mentioned "average minimum thickness",
"Average maximum thickness" refers to a value calculated as follows. That is, at an arbitrary position of the foamed sheet, a cross section cut in the width direction of the sheet orthogonal to the longitudinal direction (extrusion direction) is sliced by a microtome, and the thick part (peak part) and the thin part (valley part) of the sheet are sliced by a microscope. 10 each
The thickness was measured for each point, and arithmetic average of each was taken as “average minimum thickness” and “average maximum thickness”.

The peaks and valleys are measured at arbitrary positions except for 100 mm from both ends in the width direction of the sheet. However, the mountain part and the valley part are selected adjacent to each other. If the peaks and valleys are less than 10 points at each measurement point, the thicknesses of the existing peaks and valleys are all measured, and the arithmetic average of each of the peaks and valleys is calculated as “average minimum thickness” and “average maximum thickness”. And

In the foamed sheet of the present invention, it is essential that the value of the average minimum thickness / the average maximum thickness is 0.9 or more, and this value is preferably 0.95 or more. In the foamed sheet having this value of less than 0.9, the heating tends to be non-uniform at the time of molding, and the thin portion of the sheet tends to be thinner at the time of molding. In particular, in the case of a sheet on which a non-foamed film is laminated, the laminated film is easily peeled.

As a method for obtaining the foamed propylene-based resin sheet of the present invention, a non-crosslinked propylene-based resin having a long-chain branch and a drawdown property of 60 m / min or less in an extruder is melt-kneaded with a foaming agent. Using a circular die having an annular lip attached to the tip of the extruder, the melt-kneaded product is extruded and foamed from the lip of the die to obtain a tubular foam, and then the tube is cut open to form a sheet. Is usually adopted.

In this method, the area of the resin flow path of the circular die is preferably reduced or reduced to one or more locations by half or less, and further, a mandrel (cylindrical) for cooling the cylindrical foam extruded from the circular die. Cooling air is blown to the outer surface of the tubular foam to cool the inner and outer surfaces of the tubular foam. The value of average minimum thickness / average maximum thickness is adjusted by adopting a method such as increasing the efficiency and adjusting the throttle ratio of the flow path, the temperature of the cooling air blown to the outer surface of the tubular foam on the mandrel, the amount of spraying, and the like. However, the foamed sheet of the present invention having a value of 0.9 or more, preferably 0.95 or more can be obtained.

The narrowing of the resin flow path area of the circular die is desirably performed in the vicinity of an intermediate portion in the extrusion direction in the die, and is expressed by the cross-sectional area of the resin flow path at the narrowed portion / the same cross-sectional area immediately before narrowing. It is desirable that the aperture ratio be 4 or more.
The cooling air on the mandrel is usually 10 to 5
The temperature is set to 0 ° C. and the flow rate is set to 0.3 to ³ m ³ / min.

In producing the foamed sheet of the present invention, as the foaming agent, an inorganic foaming agent, a volatile foaming agent, a decomposable foaming agent and the like can be used. Examples of the inorganic foaming agent include carbon dioxide, air, and nitrogen.

Examples of the volatile foaming agent include aliphatic hydrocarbons such as propane, n-butane, i-butane, pentane and hexane, cycloaliphatic hydrocarbons such as cyclobutane and cyclopentane, trichlorofluoromethane and dichlorodifluoromethane. , Dichlorotetrafluoroethane, methyl chloride,
Halogenated hydrocarbons such as ethyl chloride and methylene chloride are exemplified.

Examples of the decomposable blowing agent include azodicarbonamide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, sodium bicarbonate and the like. These foaming agents can be appropriately mixed and used.

The amount of the foaming agent used varies depending on the type of the foaming agent, the desired expansion ratio, and the like, but it is necessary to obtain a preferable density of the foamed sheet of the present invention of about 0.3 to 0.06 g / cm ^3. The standard of the amount of the volatile foaming agent used is about 0.5 to 6 parts by weight (in terms of butane) per 100 parts by weight of the resin. Similarly, the amount is about 0.2 to 5 parts by weight (in terms of carbon dioxide) in the case of an inorganic foaming agent, and about 0.1 to 7.5 parts by weight in the case of a decomposable foaming agent.

In the present invention, an air conditioner is added to the melt-kneaded product of the resin and the foaming agent, if necessary. Examples of the cell regulator include inorganic powders such as talc and silica, acidic salts of polycarboxylic acids, and reaction mixtures of polycarboxylic acids with sodium carbonate or sodium bicarbonate. It is preferable to add the foam control agent in an amount of about 13 parts by weight or less per 100 parts by weight of the resin (except when a large amount of the inorganic filler is contained in the resin). Further, if necessary, additives such as a heat stabilizer, an ultraviolet absorber, an antioxidant, and a colorant can be added.

The resin may contain an inorganic filler up to 40% by weight of the total weight. Examples of the inorganic filler include talc, silica, calcium carbonate, clay, zeolite, alumina, barium sulfate and the like. It is preferable that these particles have an average particle size of 1 to 70 μm. When such an inorganic substance is contained in a large amount, the resulting foamed sheet has improved heat resistance and can reduce calorie burned during incineration.

The foamed sheet of the present invention usually has a thickness of about 0.1 to 3 mm and can be used for molding as it is, but it is used by laminating a non-foamed synthetic resin film on at least one side. You can also. Foam sheet is used for heat-softened foam sheet, vacuum forming, air pressure forming and other applications such as free drawing forming, plug and
And ridge molding, ridge molding, matched mold molding, straight molding, drape molding, reverse draw molding, air slip molding, plug assist molding, plug assist reverse draw molding, etc. be able to. The foam sheet of the present invention is particularly suitable for molding containers for microwave ovens, lunch containers, automobile ceiling materials, automobile door interior materials, trunk room members, and the like. It is also suitable as a core material for building materials.

[0038]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. In Examples and Comparative Examples, the added amounts of the foaming agent and the cell regulator are% by weight when the total amount of these and the resin is 100% by weight. To measure the drawdown property and melt tension of the used resin, use a melt indexer,
Melt tension tester II manufactured by Toyo Seiki Seisaku-sho, Ltd.
The crystallization speed was measured using a crystallization rate measuring device MK-801 manufactured by Kotaki Shoji Co., Ltd. for the measurement of the half-crystallization time.

The properties of the resins used in the examples and comparative examples are as follows.

Propylene resin A: propylene / ethylene block copolymer having a long chain branch (“SD-632” manufactured by Highmont Corporation, USA): melting point 159.9 ° C., crystallization temperature 1
30.1 ° C., half-crystallization time 1353 seconds, MI = 2.0 g / 1
0 minutes, drawdown 3.1m / min, melt tension 1
3.0gf)

Propylene resin B: propylene homopolymer having a long chain branch (“PF-81” manufactured by Highmont USA)
4 ": melting point 159.0 ° C, crystallization temperature 127.4 ° C, half-crystallization time 3220 seconds, MI = 2.2 g / 10 minutes, drawdown 3.5 m / min, melt tension 17.4 gf)

Examples 1-6, Comparative Examples 1-2 A tandem extruder (No. 1) containing the resin, foaming agent (isobutane) and foam control agent (monosodium citrate) shown in Table 1 in the proportions shown in Table 1 was used. Extruder: screw diameter 65mm, L /
D = 34, second extruder: screw diameter 90 mm, L / D =
32), melt-kneaded, and then mounted on the extruder tip at 65 mmφ (die diameter), gap (lip clear) 0.5
It was extruded into a tube from a circular die of about 1.5 mm (the resin flow area was reduced near the middle of the die in the extrusion direction. The drawing ratio was as shown in Table 1.).

The extruded and foamed tubular foam was taken in such a manner that the inner surface thereof was in contact with a cooling mandrel (mandrel diameter: 200 mm, set surface temperature: 20 ° C.). Was blown onto the outer surface of the tube to cool it, and then the tubular foam was cut open in the extrusion direction to obtain a sheet. Extrusion conditions such as extrusion foaming temperature and the obtained foamed sheet (Production 1
The properties after one week are also shown in Table 1.

In the comparative example, the die diameter and the lip clear are the same as those of the circular die of the embodiment. However, the resin flow path width is not narrowed in the vicinity of the opening of the die. No cooling air was blown onto the mandrel on the outer foam surface.

[0045]

[Table 1]

* 1: The “texture” of the foam sheet is the number of bubbles per 3 mm × 3 mm = 9 mm ² (cells / 9 mm ² ) on the foam sheet surface, and the number of bubbles is measured using a microscope. did.

Using the sheet, a tray forming test and a deep drawing test were performed under the following conditions.

[Tray Forming Test] Each sheet was clamped to the approximate center of a heating furnace having heaters of 50 W each above and below (a distance between heaters of 20 cm), continuously guided, heated, and then continuously subjected to plug-assist vacuum forming. went. The target tray-shaped container is a dish-shaped container having storage portions 2 and 3 on both sides of the partition 1 as shown in FIGS. 2 and 3. In FIGS. 2 and 3, each dimension of a to h is: a: 175 mm, b: 112
mm, c: 63 mm, d: 110 mm, e: 90 mm, f: 40
mm, g: 30 mm, h: 25 mm. The presence or absence of thickness unevenness of the obtained molded article was determined according to the following evaluation criteria, and the results are shown in Table 1.

[Evaluation Criteria for Thickness Unevenness of Molded Article] The average minimum thickness / average maximum thickness of the molded article was measured in the same manner as for the foamed sheet (excluding the condition of “excluding 100 mm from both ends in the width direction”).・: 0.95 or more ○: 0.9 or more, less than 0.95 Δ: 0.85 or more, less than 0.9 ×: less than 0.85

[Deep drawing test] Each sheet was clamped and guided to the approximate center of a heating furnace having 50 W heaters (distance between heaters: 20 cm) above and below, heated, and then continuously subjected to plug-assist vacuum forming. Was. The target molded product has a length: a = 453 mm and a width: b = 3 as shown in FIG.
In a 00 mm foam sheet 4, 45 mm deep, diameter: d =
The 80 mm hemispherical storage units 5 are arranged in four rows horizontally, and the storage units 5 are arranged in five vertical rows so that the positions of the storage units 5 are shifted by a half between the upper and lower rows. Aperture ratio is about 0.5
6. The presence or absence of thickness unevenness of the obtained molded article was determined by the same evaluation criteria as described above, and the results are shown in Table 1.

[0051]

As described above, the foamed sheet of the present invention has an average minimum thickness / average maximum thickness of 0.9 or more when the thickness of the foamed sheet is measured along the width direction. Thereby, when this foamed sheet is molded, there is no possibility that thickness unevenness occurs in the molded article, and particularly when a non-foamed film is laminated on the foamed sheet surface to form a laminated sheet, it is particularly conspicuous when the sheet is molded. It is possible to prevent the occurrence of unevenness in thickness easily and also to prevent the peeling of the film, and to obtain an excellent molded product.

[Brief description of the drawings]

FIG. 1 is a voltage-time curve obtained by crystallization rate measurement.

FIG. 2 is a plan view of a tray-shaped container formed using the foamed sheets of Examples and Comparative Examples.

FIG. 3 is a side view of a tray-shaped container formed using the foamed sheets of the examples and comparative examples.

FIG. 4 is a plan view of a deep drawn product formed using the foam sheet of each of the examples and the comparative example.

FIG. 5 is a graph showing the relationship between elongational viscosity and time at the strain rate of a propylene-based resin having long-chain branches and a propylene-based resin having no long-chain branches.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI // B29K 23:00 105: 04 B29L 9:00 C08L 23:12 (56) References JP-A-6-192460 (JP, A JP-A-2-298536 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08J 9/00-9/14 B29C 44/00-44/60 B29C 47/00-47 / 96 B32B 1/00-35/00

Claims (4)

(57) [Claims] 1. An extruded foamed sheet having a density of 0.3 to 0.06 g / cm ³ based on a non-crosslinked propylene resin having a long chain branch and a drawdown property of 60 m / min or less, When the thickness of the foamed sheet was measured along the width direction, the value of average minimum thickness / average maximum thickness was 0.9.
A propylene-based resin foam sheet characterized by the above. 2. Drawdown of non-crosslinked propylene resin
2. The propylene-based product according to claim 1, which has a property of 30 m / min or less.
Resin foam sheet. 3. Drawdown of non-crosslinked propylene resin
2. The propylene-based product according to claim 1, which has a property of 15 m / min or less.
Resin foam sheet. 4. The propion according to claim 1,
It is made by laminating a non-foamed film on a ren-based resin foam sheet
Laminated type propylene resin foam sheet.