JP2000129026A - Foamed sheet made from modified polypropylene resin composition and forming made therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a foamed sheet made from a modified polypropylene resin composition and being excellent in heat resistance, heat insulation properties, cushioning properties, and formability and to provide a forming made therefrom. SOLUTION: Provided are a foamed sheet made from a modified polypropylene resin composition obtained by melt-kneading a polypropylene resin, an isoprene monomer, and a radical polymerization initiator and being one having a density of 0.5-0.05 g/cm3, a closed-cell rate of 60% or above, a thickness of 0.8-10.0 mm, and a cell count of 1.0-5.0 in the direction of thickness, and a molecular orientation ratio of 1.0-5.0, and a forming made by forming the foamed sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a foamed sheet comprising a modified polypropylene resin composition, a molded article obtained by heat molding the same, and a method for producing the foamed sheet. More specifically, the present invention provides a foamed sheet comprising a modified polypropylene-based resin composition having excellent heat resistance, heat insulation properties, cushioning properties, and excellent moldability, and excellent heat resistance with a beautiful appearance obtained by heat molding the foamed sheet. Related to molded articles.

[0002]

2. Description of the Related Art In general, a foamed sheet made of a thermoplastic resin is light in weight, has good heat insulating properties and good buffering properties against external stress, and can easily obtain a molded article by heating and secondary molding such as vacuum molding. Since it can be used, buffer materials, food containers, heat insulating materials,
Widely used in applications such as automotive components.

[0003] However, polypropylene resins are
Since the viscosity and tensile strength at the time of melting were low, the strength of the cell wall was not sufficiently maintained at the time of foaming, and it was difficult to obtain a foamed sheet having an excellent appearance and excellent moldability. Therefore, when a foamed sheet of a polypropylene resin is subjected to heat molding such as vacuum molding, it has been difficult to obtain a good molded body.

As a method for producing a foamed sheet comprising a polypropylene-based resin composition, conventionally, a crosslinking agent, a crosslinking assistant and a pyrolytic foaming agent are added to a polypropylene-based resin, molded, and crosslinked and foamed by heating. (JP-B-45-40420), a method in which a crosslinking aid and a decomposable foaming agent are added to a polypropylene-based resin, and molding is performed, followed by radiation crosslinking, followed by heating and foaming (JP-B-42-26953). Crosslinking and foaming methods such as a method of adding a pyrolytic foaming agent to a polypropylene resin having the above and molding the mixture, followed by water foaming followed by heating and foaming (JP-A-9-132662) have been carried out.

However, the method of imparting foamability to a polypropylene resin by crosslinking requires a crosslinking step, which makes it difficult to produce a continuous foamed sheet, and it is difficult to control the degree of crosslinking, so that a uniform and beautiful sheet is obtained. There are problems that it is difficult to manufacture a foamed sheet, and furthermore, the flowability at the time of melting is remarkably reduced, so that recycling is difficult.

On the other hand, as a method for producing a foamed sheet using a non-crosslinked polypropylene resin, for example, a method using a polypropylene resin having a specific molecular weight and equilibrium compliance (Japanese Patent Publication No. 5-506875).
Have been proposed in recent years. These use resins in which long chain branches have been introduced by irradiating a polypropylene resin with radiation. However, when the polypropylene resin is modified by this method, the apparatus used is large-scale and the structure of the apparatus is inevitably complicated due to the use of radiation. Also, in the step of irradiation, to prevent decomposition and gelation of the polypropylene resin,
In order to manufacture a product stably, it is necessary to strictly control the radiation dose and the oxygen concentration of the atmospheric gas.
Therefore, it has not been easy to provide a variation in the physical properties of the target modified polypropylene resin. Further, it was not easy to obtain a foamed sheet having good moldability and capable of obtaining a molded article having the properties of a polypropylene resin.

[0007] On the other hand, conventionally, in the thermoforming of a foamed sheet made of a thermoplastic resin, a phenomenon in which the foamed sheet shrinks is observed. At that time, if the shrinkage ratio in the extrusion direction and the width direction is significantly different, the sheet may undulate during heating. If such waving is large, double waving occurs where the wavy part is formed twice during molding, and a good molded body cannot be obtained. Therefore, in a foamed sheet made of a polystyrene-based resin, as a method of suppressing waving, a method such as adjusting a shrinkage ratio during heating has been performed. However, the behavior of the foamed polypropylene resin sheet at the time of heating differs from the conventional foamed polystyrene resin sheet due to the fact that the resin is crystalline, so that the foamed sheet at the time of heating is prevented from waving and a good molded product is obtained. It is difficult to obtain a foamed sheet having good moldability or a molded article obtained by molding the foamed sheet.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a foamed sheet comprising a modified polypropylene resin composition which is capable of obtaining a molded article having excellent secondary moldability, heat resistance and heat insulation. An object of the present invention is to provide a molded article obtained by molding a foamed sheet.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a modified polypropylene obtained by melt-kneading a polypropylene resin, an isoprene monomer and a radical polymerization initiator. By specifying the foam physical properties (density, closed cell ratio, thickness, number of cells in the thickness direction) of the foamed sheet using the resin composition, and further specifying the molecular orientation ratio of the foamed sheet, It has been found that a foamed sheet excellent in formability in which the sheet is prevented from waving can be obtained, and the present invention has been completed.

That is, the present invention comprises (1) a modified polypropylene resin composition obtained by melt-kneading a polypropylene resin, an isoprene monomer and a radical polymerization initiator, and has a density of 0.5 to 0.05 g. / Cm ³ , a closed cell ratio of 60% or more, a thickness of 0.8 to 10.0 mm, a number of cells in the thickness direction of 5 or more, and a molecular orientation ratio of 1.0 to 5.0. And (2) a molded article formed by molding the foamed sheet according to claim 1 (claim 2).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The modified polypropylene resin of the present invention comprises a resin obtained by melt-kneading a polypropylene resin, an isoprene monomer and a radical polymerization initiator, and has significantly improved foamability. Things.

The modified polypropylene resin used in the present invention comprises a polypropylene resin (hereinafter, this polypropylene resin may be referred to as “raw material polypropylene resin”), an isoprene monomer, and a radical polymerization initiator. Is kneaded at a temperature at which the resin melts.

As the raw material polypropylene resin,
Crystalline polymers such as propylene homopolymers, block copolymers of propylene and other monomers or random copolymers of propylene and other monomers,
From the viewpoint of high rigidity and low cost, the polypropylene homopolymer is preferable, and from the viewpoint of high rigidity and high impact resistance, a block copolymer of the propylene and another monomer is preferable. . When the raw material polypropylene-based resin is a block copolymer of propylene and other monomers or a random copolymer of propylene and other monomers, high crystallinity and high rigidity characteristic of the polypropylene-based resin are provided. From the viewpoint of maintaining good chemical resistance, the content of the propylene monomer component is preferably at least 75% by weight, more preferably at least 90% by weight.

In the raw material polypropylene resin,
As other monomers copolymerizable with propylene, one or more selected from the group consisting of ethylene, α-olefin, cyclic olefin, diene monomer and vinyl monomer Monomers.

Of these monomers, ethylene or butene-1 is preferred because of its low cost.

The molecular weight (weight average molecular weight) of the raw material polypropylene resin is preferably in the range of 50,000 to 2,000,000 from the viewpoint of industrial availability and from 100,000 to 2,000,000 from the viewpoint of low cost. More preferably, it is within the range of 1,000,000.

If necessary, other resins or rubbers may be added to the raw material polypropylene resin within a range that does not impair the effects of the present invention. Examples of the other resin or rubber include polyethylene; polybutene-
1, poly-α-olefins such as polyisobutene, polypentene-1 and polymethylpentene-1; an ethylene / propylene copolymer having a propylene content of less than 75% by weight;
Ethylene / butene-1 copolymer, propylene content 7
Less than 5% by weight of ethylene or α-olefin / α-olefin copolymer such as propylene / butene-1 copolymer; ethylene / propylene / 5-ethylidene-2-norbornene copolymer having less than 75% by weight of propylene Ethylene or α-olefin / α-olefin / diene-based monomer copolymer such as a copolymer; ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / methacrylic acid copolymer, ethylene / acrylic acid Ethyl copolymer, ethylene / butyl acrylate copolymer, ethylene / methyl methacrylate copolymer, ethylene / maleic anhydride copolymer, ethylene / metal acrylate copolymer, ethylene / metal methacrylate copolymer Copolymer, ethylene / vinyl monomer copolymer such as ethylene / glycidyl methacrylate copolymer; poly Polydiene copolymers such as butadiene and polyisoprene; styrene / butadiene /
Vinyl monomer such as styrene block copolymer / diene monomer / vinyl monomer block copolymer; acrylonitrile / butadiene / styrene graft copolymer, methyl methacrylate / butadiene / styrene graft copolymer, etc. Vinyl monomer / diene monomer / vinyl monomer graft copolymer; polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyvinyl acetate, polyethyl acrylate, polybutyl acrylate, polymethyl methacrylate, Vinyl polymers such as polystyrene; and vinyl copolymers such as vinyl chloride / acrylonitrile copolymer, vinyl chloride / vinyl acetate copolymer, acrylonitrile / styrene copolymer, and methyl methacrylate / styrene copolymer. .

The amount of the other resin or rubber to be added to the raw material polypropylene-based resin varies depending on the type of the resin or the type of the rubber, and may be within the range that does not impair the effects of the present invention as described above. But usually
It is preferably about 25% by weight or less.

The modified polypropylene resin of the present invention is obtained by melt-kneading a polypropylene resin, an isoprene monomer, another vinyl monomer copolymerizable with the isoprene monomer, and a radical polymerization initiator. It may be manufactured.

Other vinyl monomers copolymerizable with the isoprene monomer include, for example, vinyl chloride; vinylidene chloride; styrene; acrylonitrile; methacrylonitrile; acrylamide; methacrylamide; vinyl acetate; Acid; maleic acid; maleic anhydride; metal acrylate; metal methacrylate; acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, stearyl acrylate, glycidyl acrylate; methyl methacrylate, methacrylic acid Examples include methacrylates such as ethyl, butyl methacrylate, stearyl methacrylate, and glycidyl methacrylate. When an isoprene monomer and another vinyl monomer copolymerizable with the isoprene monomer are used in combination, the amount of the other vinyl monomer copolymerizable with the isoprene monomer is limited to a single isoprene monomer. It is preferably at most 100 parts by weight, more preferably at most 75 parts by weight, based on 100 parts by weight of the body. If the amount of the other vinyl monomer copolymerizable with the isoprene monomer exceeds the above range, the viscosity of the resulting modified polypropylene resin may be significantly reduced, and the foamability may be reduced.

The amount of the isoprene monomer to be melt-kneaded is preferably 0.1 to 20 parts by weight based on 100 parts by weight of the starting polypropylene resin, and is preferably 0.3 to 20 parts by weight.
More preferably, the amount is from 10 to 10 parts by weight. If the amount of the isoprene monomer is less than the above range, the foaming property of the modified polypropylene resin may be reduced, while if it exceeds the above range, the heat resistance and rigidity characteristic of the polypropylene resin may be obtained. Etc. may be impaired.

The radical polymerization initiator generally includes a peroxide or an azo compound. Examples of the radical polymerization initiator include one or more organic peroxides such as ketone peroxide, peroxy ketal, hydroperoxide, dialkyl peroxide, diacyl peroxide, peroxydicarbonate, and peroxyester. can give. Of these,
Particularly, those having high hydrogen abstracting ability are preferable. Examples of such radical polymerization initiators include 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane and 1,1-bis (t -Butyl peroxy)
Peroxy ketals such as cyclohexane, n-butyl-4,4-bis (t-butylperoxy) valerate and 2,2-bis (t-butylperoxy) butane; dicumyl peroxide, 2,5-dimethyl- 2,5-di (t
-Butylperoxy) hexane, α, α'-bis (t-
Butylperoxy-m-isopropyl) benzene, t-
Dialkyl peroxides such as butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3; diacyl peroxides such as benzoyl peroxide; t -Butylperoxyoctate, t-butylperoxyisobutyrate, t-butylperoxylaurate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxyisopropyl carbonate, 2 , 5-Dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate, t-butylperoxybenzoate, di-t-
One or more of peroxyesters such as butyl peroxyisophthalate may be used.

The amount of the radical polymerization initiator to be added is from 0.1 to 10 parts by weight based on 100 parts by weight of the starting polypropylene resin from the viewpoint of good foaming property of the modified polypropylene resin and economical viewpoint. It is preferably within the range, more preferably within the range of 0.2 to 5 parts by weight.

Further, if necessary, an antioxidant, a metal deactivator, a phosphorus-based processing stabilizer, an ultraviolet absorber, an ultraviolet stabilizer, a fluorescent whitening agent, a metal soap, an antacid Additives such as stabilizers such as adsorbents or additives such as crosslinking agents, chain transfer agents, nucleating agents, lubricants, plasticizers, fillers, reinforcing materials, pigments, dyes, flame retardants, antistatic agents, etc. You may add in the range which does not impair.

The order and method of mixing or melt-kneading the raw material polypropylene resin, isoprene monomer, radical polymerization initiator and other added materials are not particularly limited. The monomer, the radical polymerization initiator and other additives added as necessary may be mixed and then melt-kneaded, or the raw material polypropylene-based resin, the radical polymerization initiator and other components added as necessary May be melt-kneaded with the isoprene monomer after melt-kneading, or after the modified polypropylene resin is obtained by the above-described method, melt-kneading with additives and other resins added as necessary. After further modifying a part of the raw polypropylene to form a master batch, the remaining raw polypropylene A pyrene-based resin may be melt-kneaded.

The heating temperature at the time of melt kneading varies depending on the type of the resin, but it is usually from 130 to 400 ° C. that the raw polypropylene resin is sufficiently melted, does not thermally decompose, and has a sufficient foaming property. Is preferred in that it is possible to obtain The time for melt-kneading (the time after mixing the radical polymerization initiator and the isoprene monomer) is generally 30 seconds to 60 minutes.

Examples of the melt kneading apparatus include kneaders such as a co-kneader, a Banbury mixer, a Brabender, a single-screw extruder, a twin-screw extruder, a twin-screw surface renewer, and a twin-screw multi-disc apparatus. There is a device such as a horizontal stirrer or a vertical stirrer such as a double helical ribbon stirrer capable of heating a polymer material to an appropriate temperature and kneading while applying an appropriate shear stress. Among these, a single-screw or twin-screw extruder is particularly preferred in terms of productivity. In addition, the melt-kneading may be repeated a plurality of times in order to sufficiently and uniformly mix the respective materials.

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

The foamed sheet made of the modified polypropylene resin composition of the present invention is prepared by, for example, melt-kneading the modified polypropylene resin composition and the foaming agent in an extruder, and then adjusting the foaming optimum temperature in the extruder. Using a circular die having an annular lip, extruding from the lip of the die into atmospheric pressure to obtain a cylindrical foam,
Next, while taking up the cylindrical foam, a method of forming by a cooling cylinder (mandrel), stretching and cooling, and then cutting out to form a sheet, or a decomposition type foaming agent that generates gas by heating with a modified polypropylene resin and heating After melt-kneading and shaping into a sheet, the foaming agent is easily decomposed to generate gas and foam to produce easily. Further, extrusion foaming / foaming molding may be performed continuously with the production of the modified polypropylene resin composition.

As a device for kneading the modified polypropylene resin and the decomposable foaming agent, a roll, a co-kneader,
Kneaders such as Banbury mixers, Brabenders, single-screw extruders, twin-screw extruders, horizontal stirrers such as twin-screw renewers, twin-screw multi-disc devices, and vertical stirrers such as double helical ribbon stirrers; And the like. Of these, rolls and extruders are particularly preferred in terms of productivity.

Examples of the foaming agent include aliphatic hydrocarbons such as propane, butane, pentane, hexane and heptane; alicyclic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane; chlorodifluoromethane;
Difluoromethane, trifluoromethane, trichlorofluoromethane, dichloromethane, dichlorofluoromethane, dichlorodifluoromethane, trichlorofluoromethane, chloromethane, chloroethane, dichlorotrifluoroethane, dichlorofluoroethane, chlorodifluoroethane, dichloropentafluoroethane, tetrafluoroethane, Halogenated hydrocarbons such as difluoroethane, pentafluoroethane, trifluoroethane, dichlorotetrafluoroethane, trichlorotrifluoroethane, tetrachlorodifluoroethane, chloropentafluoroethane and perfluorocyclobutane; inorganics such as carbon dioxide, nitrogen and air Gas; one or more of water and the like.

The addition amount (kneading amount) of the foaming agent varies depending on the type of the foaming agent and the target expansion ratio, but is 0.5 to 10 parts by weight based on 100 parts by weight of the polypropylene resin composition.
Preferably it is in the range of parts by weight.

If necessary, a foam nucleating agent such as sodium bicarbonate-citric acid or talc may be used in order to control the cell diameter of the foam sheet to an appropriate size. The amount of the foaming nucleating agent used as needed is,
Usually, it is preferably 0.01 to 3 parts by weight based on 100 parts by weight of the modified polypropylene resin.

The foamed sheet made of the modified polypropylene resin composition according to the present invention may be, for example, extruded and foamed to promote cooling by air blowing or the like to obtain a desired cell structure, or to provide a mandrel. It may be stretched at the time of taking back.

The density of the foamed sheet comprising the modified polypropylene resin composition in the present invention is 0.5 to 0.05 g.
/ Cm ³ preferably is preferably 0.3～0.06G / cm ³ further 0.2～0.08G / cm ^3.
When it is smaller than 0.05, the rigidity is poor, and when it is larger than 0.5, the heat insulating property is poor.

In the foamed sheet made of the modified polypropylene resin composition of the present invention, when heated and molded,
If the thickness of the next foam is not ensured, a good molded product cannot be obtained due to poor mold determination in the mold. This secondary foaming is caused by expansion of the closed cells of the foam sheet. From the above points, the closed cell rate is 60% or more, preferably 70% or more, and more preferably 80% or more.
% Or more is preferable. In the case of 60% or less, the secondary expansion ratio at the time of heat molding becomes small, and the mold rule is poor.
Good moldability cannot be obtained.

The thickness of the foamed sheet made of the polypropylene resin composition in the present invention is 0.8 to 10 mm, more preferably 1 to 5 mm. When it is smaller than 0.8, the heat insulation, rigidity and cushioning property are degraded, and when it is larger than 5 mm, the moldability is reduced. The number of cells is preferably 5 and more preferably 7 or more. When the number is smaller than 5, the heat insulating property and the surface property are inferior.

In a foamed sheet made of the modified polypropylene resin composition, the base resin is melted by heating during molding, and at the same time, the gas in the cell expands. Therefore, a flat cell tends to turn into a sphere. At this time, the diameter of the cell in the short axis direction tends to increase, and the diameter in the long axis direction tends to decrease. Therefore, the amount of shrinkage of the cells in the sheet due to heating in the short-axis direction and the long-axis direction is different, so that waving or the like occurs. Accordingly, the present inventors have conducted intensive studies and found that a foamed sheet having good moldability can be obtained by defining the molecular orientation ratio of the foamed sheet and suppressing waving during molding heating. The invention has been completed.

The foamed sheet made of the modified polypropylene resin composition of the present invention has a molecular orientation ratio of 1.0 to 5.0.
0. Here, the molecular orientation ratio is a value measured by a molecular orientation meter (MOA-3001A manufactured by Oji Scientific Instruments). If it exceeds 5.0, the waving during molding heating is large,
Wrinkles due to double hitting during molding tend to occur in the molded body.

The foamed sheet made of the modified polypropylene resin composition of the present invention is excellent in heat moldability such as plug molding, vacuum molding and pressure molding, so that a molded article having a small thickness unevenness and a beautiful appearance can be obtained. be able to.

Examples of heat molding include plug molding, matched molding, straight molding, drape molding,
Examples include plug assist molding, plug assist / reverse draw molding, air slip molding, snapback molding, reverse draw molding, free drawing molding, plug and ridge molding, and ridge molding.

The heat moldability of the foamed sheet made of the modified polypropylene resin composition is adjusted, for example, by placing the clamped foamed sheet in an oven set at 350 ° C., preheating it for 25 seconds, and then adjusting the temperature to 38 ° C. The outer diameter of the opening is 100 mm and the outer diameter of the bottom is 6
It can be evaluated by preparing a cup-shaped molded body having a height of 0 mm and a height of 40 mm. In other words, a molded article obtained from a foamed sheet having excellent secondary moldability has a good appearance, but a molded article obtained from a foamed sheet having poor secondary moldability has many irregularities and streaks on its surface, and in some cases, it has a severe uneven wall thickness. Will not endure.

In the heat molding, the foamed sheet is molded after preheating, and the density, thickness and closed cell rate may change due to secondary foaming of the foamed sheet during the preheating. is there.

The foamed sheet made of the modified polypropylene resin composition of the present invention has good surface properties and rigidity. For the purpose of improving the heat moldability and the like, a film or sheet-like non-foamed layer (hereinafter referred to as a laminating layer) made of a thermoplastic resin may be formed on at least one surface of the foamed sheet.

As the thermoplastic resin used for the laminating layer, methyl methacrylate resin, polystyrene resin,
Polypropylene resin, polyethylene resin, polyethylene terephthalate resin, polybutylene terephthalate, polyamide (nylon) resin, polycarbonate resin, polyarylate resin, polyimide resin, polyether sulfone resin, polysulfone resin, vinyl chloride resin Resins, and these may be used alone or in combination of two or more.

The lamination layer may be a foamed resin.

When forming the thermoplastic resin laminating layer,
The base resin of the laminating layer may contain, if necessary, an impact resistance improver, a filler, a lubricant, an antioxidant, an antistatic agent, a pigment, a stabilizer, an odor reducing agent, a flame retardant, a bubble regulator, etc. May be added alone or in combination of two or more.

As a method for forming the laminating layer, a method in which a resin previously formed into a film or a sheet is foamed and bonded to one or both sides of a foamed sheet supplied and supplied with a hot roll or the like, Of resin molded into a foam into one or both sides of a foamed sheet that is foamed and supplied via an adhesive, coextrusion lamination using a multilayer extrusion die, foaming that is foamed and supplied in advance There is a method in which a laminating layer resin composition supplied from an extruder is laminated in a layer on one or both sides of a sheet, and the plasticizing laminating layer is fixed by a cooling roller or the like. Above all, a method in which the production of the foamed sheet and the lamination of the non-foamed layer are performed in-line and laminated is preferable in terms of the number of production steps and the cost.

A molded article can be obtained from the foamed laminated sheet by molding in the same manner as the foamed sheet.

[0050]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. (1) Measurement of density of foamed sheet Measured according to JIS-K6767. (2) Measurement of closed cell rate of foamed sheet Measured with an air pycnometer according to the method described in ASTM D-2856. (3) Thickness measurement of foam sheet Ten measurement points are provided at equal intervals in the width direction of the foam sheet,
After measuring the thickness of the measurement point using a thickness gauge (a thickness gauge manufactured by Teklock), the average of the measured values at each point was defined as the thickness of the foamed sheet. (4) Measurement of the number of cells in the thickness direction of the foam sheet Measurement points are provided at intervals of 30 mm in the width direction of the foam sheet, and the number of cells in the thickness direction at the measurement points is measured using a loupe (peacoc).
The measurement was performed using a pocket micro (manufactured by K Company). Thereafter, the average of the measured values at each point was defined as the number of cells in the thickness direction. (5) Measurement of cell flatness of foam sheet 100 × 95 m at 100 mm intervals in the width direction of foam sheet
m samples were cut out, and the molecular orientation ratio of each sample was measured with a molecular orientation meter (Oji Scientific Instruments MOA-3001A), and the average of the measured values was defined as the molecular orientation ratio of the foamed sheet. (6) Evaluation of Formability The following criteria were visually evaluated. ×: Large undulation was observed at the time of molding and heating, and double dent was observed in the obtained molded article.

△: Small undulation is observed at the time of molding heating, and double undulation is observed in the obtained molded body.

：: Small undulation was observed during molding heating, and no double dent was observed in the obtained molded body.

A: No undulation is observed at the time of molding and heating, and no double dent is observed in the obtained molded article. (7) Molded product evaluation The molded product was evaluated by visual observation and sensitivity evaluation as follows.

A: The molded product has good mold definition and sufficient rigidity.

：: In the molded product, the molding was well determined and the rigidity was insufficient. Alternatively, the mold is inconsistent and has sufficient rigidity.

×: The molded product has poor mold determination and insufficient rigidity. Example 1 Propylene homopolymer (B10 manufactured by Grand Polymer Co., Ltd.)
1W) 100 parts by weight of a radical polymerization initiator (Nippon Oil & Fats Co., Ltd., Perbutyl I) was stirred and mixed with a ribbon blender in a ribbon blender. TEX44XCT-38), and isoprene was fed from the middle of the extruder at a rate of 2.5 parts by weight to 100 parts by weight of the propylene homopolymer using a liquid addition pump. By melt-kneading and melt-extruding, pellets of the modified polypropylene resin were obtained.

The twin-screw extruder was of the same-direction twin-screw type, had a screw diameter of 44 mmφ, and had a maximum effective screw length (L / D) of 38. The set temperature of the cylinder of this twin-screw extruder should be 1 until the isoprene monomer is injected.
The temperature was set to 80 ° C., 200 ° C. after the injection of isoprene, and the screw rotation speed was set to 150 rpm.

100 parts by weight of the modified polypropylene resin, 0.05 parts by weight of the blended oil, and 0.1 part by weight of a cell nucleating agent (Serubon SC / K manufactured by Eiwa Industries Co., Ltd.) were stirred and mixed by a ribbon blender. Is supplied to a 65-90 mmφ tandem type extruder and melted in a first-stage extruder (65 mmφ) set at 200 ° C., and isobutane as a foaming agent is added to 100 parts by weight of the modified polypropylene resin. 2.0 parts by weight.
2. Cooled in a second-stage extruder (90 mmφ) set at 5 ° C, discharged from a circular die (100 mmφ) under atmospheric pressure, and formed with a cooling cylinder having a diameter of 205 mm.
Stretching and cooling while taking it at 1 m / min to obtain a cylindrical foam, which is cut open with a cutter to obtain 635 mm
A foam sheet having a width was obtained.

When this foamed sheet was evaluated, the density was 0.182 g / cm 3, the closed cell ratio was 91%, the number of cells in the thickness direction was 10, the thickness was 2.0 mm, and the molecular orientation ratio was 1.26.

The foamed sheet was clamped, and the foamed sheet was placed in an oven set at 350 ° C., preliminarily heated for 25 seconds, and then the clearance adjusted to 38 ° C.
The outer diameter of the opening is 10 by plug molding using a 5 mm mold.
A cup-shaped molded body having a thickness of 0 mm, a bottom outer diameter of 60 mm, and a height of 40 mm was prepared, and the heat moldability was evaluated from the appearance of the obtained molded body according to the above criteria. The free thickness of the foamed sheet at the time of molding and heating was 3.2 mm. Table 1 shows the evaluation results. Example 2 A foamed sheet was obtained in the same manner as in Example 1 except that the take-up speed of the sheet during production of the foamed sheet was 4.5 m / min. When this foamed sheet was evaluated, the density was 0.143 g / cm ³ , the closed cell ratio was 88%, and the number of cells was 9
Each had a thickness of 1.6 mm and a molecular orientation ratio of 3.98. Next, a molded article was obtained in the same manner as in Example 1 except that the preliminary heating time was set to 23 seconds, and the heat moldability was evaluated. 2.5m free thickness when foaming sheet is heated
m. The evaluation results are shown in Table 1. Comparative Example 1 A foamed sheet was obtained in the same manner as in Example 1 except that the take-up speed of the sheet during production was 6.0 m / min. When this foamed sheet was evaluated, the density was 0.150 g / cm ³ , the closed cell ratio was 77%, and the number of cells was 7
Each had a thickness of 0.8 mm and a molecular orientation ratio of 6.23. Next, a molded body was obtained in the same manner as in Example 1 except that the preheating time was 20 seconds and the mold clearance was 1 mm, and the heat moldability was evaluated. The free thickness of the foam sheet at the time of molding and heating was 1.4 mm. The evaluation results are shown in Table 1. Comparative Example 2 Instead of the modified polypropylene resin of Example 1, a propylene homopolymer (B101W manufactured by Grand Polymer) was used.
A foamed sheet was obtained in the same manner as in Example 1 except for using. When this foam sheet was evaluated, the density was 0.251.
g / cm 3, closed cell ratio 18%, number of cells 13, thickness 0.9 mm, molecular orientation ratio 2.58.

A molded product was obtained in the same manner as in Example 1 except that the mold clearance was set to 1 mm, and the heat moldability was evaluated. The free thickness of the foam sheet at the time of molding and heating was 1.0 mm. Table 1 shows the evaluation results.

[0062]

[Table 1] It can be seen that in the foamed sheet having an aspect ratio of 1 or more and 5 or less in the examples, the sheet does not undulate at the time of heating, the formability is good, and a sufficiently acceptable molded body can be obtained. As can be seen from Comparative Example 2, a sheet having a low closed cell ratio cannot provide a sufficient molded body.

[0063]

The foamed sheet made of the modified polypropylene resin composition of the present invention has a beautiful appearance and excellent moldability, and can provide a good molded article even after the secondary molding.

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Claims (2)

[Claims] 1. A modified polypropylene resin composition obtained by melt-kneading a polypropylene resin, an isoprene monomer and a radical polymerization initiator, and having a density of 0.5 to 0.5.
05g / cm ³ , closed cell rate 60% or more, thickness 0.8 ~
What is claimed is: 1. A foamed sheet comprising a modified polypropylene-based resin composition, which is 10.0 mm and has 5 or more cells in a thickness direction, wherein the molecular orientation ratio is 1.0 to 5.0. 2. A molded article obtained by molding the foamed sheet according to claim 1.