JP2000289082A - Manufacture of modified polypropylene resin foamed sheet, foamed sheet and molded object thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polypropylene resin foamed sheet having excellent secondary processability and a high closed-cell ratio, the foamed sheet obtained by this method and a molded object molded from the foamed sheet. SOLUTION: A polypropylene resin, an isoprene monomer and a radical polymn. initiator are melted to be kneaded and a foaming agent is introduced into the resulting mixture under pressure to be kneaded therewith and the obtained compsn. is extruded to a low pressure zone from a mold having an annular slit while cooled to continuously perform the modification of the polypropylene resin and extrusion foaming to obtain a foamed sheet. This foamed sheet is thermoformed to obtain a molded article.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a foamed sheet comprising a modified polypropylene resin composition, a foamed sheet, and a molded article obtained by subjecting the foamed sheet to heat molding.

[0002]

2. Description of the Related Art A foamed sheet made of a thermoplastic resin is generally light in weight, has good heat insulating properties and good buffering properties against external stress, and can be formed into a molded article by heat molding such as vacuum molding. It is widely used in applications such as cushioning materials, food containers, heat insulating materials, and automobile parts, mainly using polystyrene resins and polyethylene resins.

[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 a high closed cell rate. In addition, 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 foaming property to PP by crosslinking requires a crosslinking step, and it is difficult to control the degree of crosslinking, so that it is difficult to continuously produce a foamed sheet, and a uniform and beautiful foamed sheet is required. Manufacturing was difficult. Further, the crosslinked PP foam has a problem that it is difficult to recycle because the flowability at the time of melting is significantly reduced.

On the other hand, as a method for producing a foamed sheet using non-crosslinked polypropylene, for example, a method using a polypropylene resin having a specific molecular weight and equilibrium compliance (Japanese Patent Publication No. 5-506875) has recently been proposed. I have. According to the detailed description and Examples, a resin having a long chain branch introduced by irradiating a radiation to a polypropylene-based resin commercially available as a high melt strength resin is used.

However, when the polypropylene resin is modified by this method, since the radiation is used, the equipment used becomes large-scale, and the structure of the equipment is inevitably complicated. In addition, in the step of irradiation, to prevent decomposition and gelation of the propylene-based 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.
In addition, since it is necessary to strictly control the production conditions in this way, it is not easy to make the physical properties of the target modified polypropylene resin composition vary.

Further, during extrusion foaming of a high melt tension resin, the resin is deteriorated in the process of melting the resin pellets, and the melt viscosity is lowered. Due to the decrease in the melt viscosity, it is difficult to maintain the resin pressure in the mold, it is difficult to control foaming in the mold, and the resulting foamed sheet has a low closed cell ratio, magnification, thickness, and surface However, there is a problem that the foam sheet becomes bad. On the other hand, there is a problem that the sheet hangs down by its own weight during heating in the secondary molding of the polypropylene resin foam sheet. In order to prevent sagging due to its own weight, it is desirable to use a foamed sheet made of a resin having a high melt viscosity, but since there is a phenomenon in which the melt viscosity decreases due to deterioration of the resin as described above, the desired melt viscosity is reduced. It was difficult to obtain a foamed sheet made of a resin having the same.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a foamed sheet excellent in moldability, which is capable of continuously and easily producing a non-crosslinked modified polypropylene-based resin foamed sheet.
It is an object of the present invention to obtain an excellent molded product obtained by the subsequent molding.

[0010]

According to the present invention, (1) a mixture comprising a polypropylene resin, a radical polymerization initiator, and an isoprene monomer is supplied to an extruder, and the radical polymerization initiator is substantially decomposed. Kneading at a temperature that can be performed to form a melt-kneaded body, a foaming agent is pressed into the melt-kneaded body, and the melt-kneaded body into which the blowing agent has been pressed is cooled to a temperature suitable for foaming. Is extruded into a low-pressure area through a mold having an annular slit, foamed into a cylinder, stretched and cooled by a cooling cylinder, cut open, and taken up in a sheet-like resin. (Claim 1) for producing a modified polypropylene resin foam sheet in which reforming and extrusion foaming are continuously performed, and (2) an extruder comprising a polypropylene resin, a radical polymerization initiator, and an isoprene monomer. The mixture is supplied, and the mixture is kneaded at a temperature at which the radical polymerization initiator can be substantially decomposed into a melt-kneaded body. A foaming agent is press-fitted into the melt-kneaded body, and the melt-kneading is performed with the foaming agent press-fitted. After the body is cooled to a temperature suitable for foaming, the melt-kneaded body is extruded into a low-pressure region through a mold having an annular slit and foamed into a cylinder, and the tubular foam is stretched and cooled in a cooling cylinder. The foamed sheet (Claim 2), which is obtained by cutting open and taking the sheet, (3) the resin composition constituting the foamed sheet is 180 ° C., and the shear rate is 122 /
The foamed sheet according to claim 2, wherein the melt viscosity in sec is 800 to 3000 Pa · s (claim 3), (4) the density is 0.5 to 0.05 g / cm ³ , the closed cell rate is 60% or more,
The foamed sheet according to claim 2 or 3, wherein the thickness is 0.8 to 10.0 mm and the number of cells in the thickness direction is 5 or more (claim 4), (5) a polypropylene resin, a radical polymerization initiator, A mixture comprising an isoprene monomer is supplied, and the mixture is kneaded at a temperature at which the radical polymerization initiator can be substantially decomposed into a melt-kneaded product. The press-fitted melt-kneaded body is cooled to a temperature suitable for foaming, and the melt-kneaded body is extruded into a low-pressure region through a mold having an annular slit and foamed into a cylindrical shape. After being stretched and cooled, the sheet is cut open, and the density is 0.5 to
0.05 g / cm ³ , closed cell rate of 60% or more, thickness of 0.
A molded product obtained by heating and molding a foamed sheet having 8 to 10.0 mm and 5 or more cells in the thickness direction in a heating furnace (claim 5), (6) a resin composition constituting the foamed sheet, 18
The melt viscosity at 0 ° C. and a shear rate of 122 / sec is 800
The molded product according to claim 5, wherein the pressure is from 3,000 Pa · s to 3,000 Pa · s.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The modified polypropylene resin composition of the present invention comprises a resin obtained by melt-kneading a polypropylene resin, an isoprene monomer and a radical polymerization initiator. Is what it is. The present invention is characterized in that, in the production of a foamed sheet made of a modified polypropylene resin, the production of the modified polypropylene resin and extrusion foaming are continuously performed.

[0012] By continuously performing the reforming and extrusion foaming of the polypropylene-based resin, the shearing during the melting process of the modified polypropylene in the extruder is omitted, and the deterioration of the resin at that time is eliminated. Extrusion foaming can be performed without impairing the foamability of the resin, and as a result, a good foam can be obtained. Further, by performing the steps continuously, the number of steps is reduced, and the productivity and cost are excellent.

There is no particular limitation on the method of supplying the mixture comprising the polypropylene resin, the isoprene monomer and the radical polymerization initiator to the extruder. For example, an isoprene monomer and a radical polymerization initiator may be supplied together with the polypropylene-based resin, or after the polypropylene-based resin is supplied to the extruder, the isoprene monomer and the radical polymerization initiator are supplied from the middle of the extruder. Simultaneously or separately,
They may be supplied collectively or dividedly.

The extruder in the present invention is not particularly limited. For example, a tandem-type extruder in which the first stage is a twin-screw extruder and the second stage is a single-screw extruder may be used, or only the twin-screw extruder may be used. Is also good.

In the melt-kneading process of the polypropylene resin, the isoprene monomer and the radical polymerization initiator, a twin-screw extruder is preferred, because a graft copolymerization reaction can be uniformly performed on the polymer molecules.
More preferably, the screws are co-rotating and completely meshing. The co-rotating type means that two screws rotate in the same direction, and the completely meshing type means that the center-to-center distance of the two screws in the extruder is smaller than the sum of the radii of the two screws. Refers to a structure.

Subsequently, at a temperature at which the polypropylene resin can be melted in the extruder and the radical polymerization initiator can be substantially decomposed, the polypropylene resin, isoprene monomer, radical polymerization By melting and kneading with an initiator, an isoprene monomer is graft-copolymerized with polymer molecules of the polypropylene resin.

The temperature at which the radical polymerization initiator can be substantially decomposed means that the radical polymerization initiator thermally decomposes and releases radicals, and the radicals work effectively to convert the isoprene monomer into the polypropylene resin. Temperature required to start graft copolymerization with the polymer molecules of Also,
The temperature during the melt-kneading is a temperature at which the radical polymerization initiator is decomposed and the resin is not thermally decomposed. The temperature depends on the type of the initiator, but is usually 160 to 400 ° C., preferably 180 ° C.
The temperature is appropriately selected in the range of ~ 300 ° C.

The time required for melt-kneading is such that the polypropylene resin, the isoprene monomer and the radical polymerization initiator are mixed with each other because a sufficient graft copolymerization reaction occurs between the polypropylene resin and the isoprene monomer. It is preferable that the mixing time is 20 seconds to 60 minutes after mixing.
More preferably, the time is from 0 seconds to 50 minutes.

Subsequently, there is no particular limitation on the method of press-fitting the foaming agent into the melt-kneaded product.

The melt-kneaded body into which the foaming agent has been pressed is cooled to a temperature suitable for foaming. The temperature is a temperature capable of maintaining viscoelasticity that can withstand the growth of bubbles when the melt-kneaded body into which the foaming agent is pressed is foamed, and such a temperature is relative to the melting point of the melt-kneaded body. -25 ° C ~
It is usually in the range of + 10 ° C.

Further, the melt-kneaded body cooled to a temperature suitable for foaming is foamed by being extruded through a mold having an annular slit, for example, under a low-pressure atmosphere of about normal pressure, thereby obtaining a modified polypropylene resin foam. . The pressure of the resin in the mold at that time is preferably 1.5 MPa or more. When the pressure is smaller than 1.5 MPa, the cells have a tendency to break.

The obtained foam is stretched by a cooling cylinder.
Cooled. The temperature of the cooling cylinder is preferably maintained at 60 ° C. or lower in order to prevent the fusion of the foam to the cooling cylinder. For the purpose of preventing fusion to the cooling cylinder and obtaining a desired cell structure, for example, air or the like may be sprayed on the surface of the foam sheet immediately after extrusion foaming.

The modified polypropylene resin used in the present invention is obtained by melting a polypropylene resin as a raw material (hereinafter sometimes referred to as a “raw polypropylene resin”), an isoprene monomer and a radical polymerization initiator. It is obtained by kneading under temperature.

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 it is inexpensive.

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 polypropylene resin as long as the effects of the present invention are not impaired. 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 / vinyl monomer copolymers such as ethylene / metal methacrylate copolymer and ethylene / glycidyl methacrylate copolymer; polydiene copolymers such as polybutadiene and polyisoprene; styrene / butadiene / styrene block copolymer Vinyl monomers such as union / diene monomer / vinyl monomer block copolymer; vinyl monomers such as acrylonitrile / butadiene / styrene graft copolymer, methyl methacrylate / butadiene / styrene graft copolymer / Diene monomer / vinyl monomer graft copolymer; polyvinyl chloride, polyvinylidene chloride,
Vinyl polymers such as polyacrylonitrile, polyvinyl acetate, polyethyl acrylate, polybutyl acrylate, polymethyl methacrylate, and polystyrene; vinyl chloride /
Examples include vinyl copolymers such as 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 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 is used in combination with another vinyl monomer copolymerizable with the isoprene monomer,
The amount of the other vinyl monomer copolymerizable with the isoprene monomer is 1 to 100 parts by weight of the isoprene monomer.
It is preferably at most 00 parts by weight, more preferably at most 75 parts by weight on average. 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, and more preferably 0.1 to 20 parts by weight, based on 100 parts by weight of the starting polypropylene resin.
More preferably, it is 0 parts by weight. When the amount of the isoprene monomer is less than 0.1 part by weight, the foaming property of the modified polypropylene resin may be low. On the other hand, when the amount is more than 20 parts by weight, the heat resistance and the characteristic of the polypropylene resin may be reduced. Rigidity 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 0.1 to 10 parts by weight based on 100 parts by weight of the raw material polypropylene-based resin because the foaming property of the modified polypropylene-based resin is good and economical. It is preferably in the range of parts by weight, more preferably in 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 brightener, 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 the raw material polypropylene resin, isoprene monomer, radical polymerization initiator and other materials to be added are not particularly limited. For example, the raw material polypropylene resin, isoprene monomer , May be melt-kneaded after mixing the radical polymerization initiator and other additional materials added as necessary, or may be a raw material polypropylene-based resin, a radical polymerization initiator and other additional materials added as necessary May be melt-kneaded and then the isoprene monomer may be melt-kneaded.

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 100 parts by weight of the modified polypropylene resin composition.
Preferably it is in the range of 10 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 1 part by weight based on 100 parts by weight of the modified polypropylene resin composition.

The modified polypropylene resin of the present invention
The density and closed cell rate of the foam sheet made of the composition
Therefore, it can be appropriately selected, but the density is 0.5 to 0.05 g /
cm ^ThreeThat the closed cell rate is 60% or more,
It is preferred because it is excellent in weight, lightweight and does not impair rigidity
No.

The density of the foamed sheet comprising the modified polypropylene resin composition of 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.
If less than 0.05 g / cm ³ , the rigidity is poor,
When it is more than 0.5 g / cm ³ , the heat insulation property is poor.

In the modified PP resin foam sheet of the present invention, if the secondary foam thickness is not ensured during heating and molding, the molding of the mold is poor and a good molded article cannot be obtained. This secondary foaming is caused by expansion of closed cells of the foam sheet. Therefore, the closed cell rate is preferably 60% or more, more preferably 70% or more, and further preferably 80% or more. If it is 60% or less, the secondary expansion ratio during heat molding is small, the mold is not fixed properly, and good moldability cannot be obtained.

The thickness of the foamed sheet made of the modified polypropylene resin composition in the present invention is 0.8 to 10 mm.
And more preferably 1 to 5 mm. 0.8mm
The smaller the size, the lower the heat insulation, rigidity and cushioning.
If it is larger than mm, the moldability is poor. The number of cells is preferably 5 and more preferably 7 or more. If the number is smaller than 5, the fusion to the cooling cylinder at the time of molding with the cooling cylinder is large and it is difficult to form a sheet, and at the same time, the heat insulating property and the surface property are poor.

The foamed sheet made of the modified polypropylene resin composition of the present invention is excellent in heat molding 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 polypropylene resin composition is, for example, as follows.
The foamed sheet clamped to a 0 mm clamp is heated to 350 ° C.
Can be evaluated based on the maximum amount of sag when pre-heated for 60 seconds in an oven set at. When the amount of sag is large, when the foamed sheet heated in the heating furnace is guided to the molding die, it contacts the heating furnace shutter or the mold and a good molded body cannot be obtained. In some cases, double stamping may occur. From the above points, the amount of sag is preferably 30 mm or less.

In the above-mentioned heat molding, the foamed sheet is formed 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.

In the present invention, the polypropylene-based resin composition constituting the foamed sheet has a shear rate of 122 ° C. and a temperature of 180 ° C.
/ Sec is 800 Pa · s to 3000
Pa · s, preferably 900 Pa · s to 3000 Pa · s
s. When it is smaller than 800 Pa · s, the sag amount is larger than 30 mm in the above-mentioned evaluation of the moldability, and the moldability tends to be inferior. Also 3000
If it is larger than Pa · s, the sheet tends to be broken at the time of secondary molding due to poor elongation.

The melt viscosity of the resin composition constituting the foamed sheet is measured by the following method. Vacuum dryer (VOS-450S, manufactured by Tokyo Rika Kikai Co., Ltd.)
In D), the temperature was raised from room temperature to 170 ° C. in about 1 hour at a vacuum pressure of 76 mmHg, maintained at 170 ° C. for 1 hour, and then lowered to room temperature in about 3 hours to obtain a sample for melt viscosity measurement. . Next, the obtained sample was measured for melt viscosity using a capillograph (manufactured by Toyo Seiki Co., Ltd., capillograph). Fill into a barrel (9.55 mm in diameter, 250 mm in length) set at 180 ° C.
Preheating for 10 minutes, lowering the piston at a speed of 10 mm / min
The melt viscosity was measured by calculating from the stress applied to the piston when extruded from a capillary (diameter 1 mm x length 10 mm) at (shear rate 122 / sec).

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

The laminating layer may be formed by a method in which a resin previously formed into a film or sheet is bonded to one or both sides of a foamed sheet which is foamed and supplied by 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 cost.

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

[0057]

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 foam 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. (6) Evaluation of sagging amount Measured by the method described in the specification. (7) Molded product evaluation Opening (oval: major axis 120 mm x minor axis 100 mm),
The molded body was evaluated using a mold having a bottom (elliptical shape: major axis 100 mm × minor axis 80 mm), depth (40 mm), and mold clearance of 1.5 mm. ：: 10 or less molded articles where double hitting is observed ×: 10 or more molded articles where 2 or more double impacting is observed (8) Resin composition for foam sheet Melt viscosity evaluation Measured by the method described in the specification. Example 1 Polypropylene resin (manufactured by Grand Polymer Co., Ltd., F
109BA), 100 parts by weight of a radical polymerization initiator (Perbutyl I, manufactured by NOF Corporation), and 0.1 parts of sodium bicarbonate-citric acid (Serubon SC / K, manufactured by Eiwa Chemical Co., Ltd.)
Parts by weight in a ribbon blender, and 0.5 parts by weight of an isoprene monomer were added to the mixture. The first-stage extruder was used for a cylinder having a diameter of 32 mm and a maximum effective screw length (L / D) of 25.5. Of the tandem type extruder comprising a single screw extruder having a cylinder diameter of 50 mmφ, and a co-rotating twin screw extruder (LABOTEX manufactured by Japan Steel Works, Ltd.) The mixture is supplied to a twin-screw extruder, the heating temperature is set to 200 ° C., the screw speed is set to 80 rpm, the discharge rate is set to 10 kg / hr, and the mixture is melt-kneaded to graft copolymerize the isoprene monomer to the polypropylene polymer molecule. From the blowing agent pressure inlet provided in the middle of the cylinder of the twin screw type extruder, isorich butane (iso / n =
85/15% by weight) at a rate of 2.0 parts by weight (0.2 kg / hr) with respect to 100 parts by weight of the melt-kneaded body, further melt-kneaded, and continuously single-stage extrusion of the second stage. Sent to the device. Next, in the second-stage single-screw extruder, the melt-kneaded body was cooled so that the temperature became 160 ° C., extruded at a screw rotation speed of 8 rpm, and attached to the tip of the second-stage single-screw extruder. The mixture was passed through an annular slit mold (diameter: 75 mmφ) controlled at 160 ° C. to obtain an extruded tubular foam. The obtained tubular foam was stretched and cooled in a cooling cylinder (diameter: 150 mmφ) whose temperature was controlled at 25 ° C., and was cut open by a cutter to obtain a drawn foam sheet at a drawing speed of 1.5 m / min.

The obtained foamed sheet was evaluated. Table 1 shows the evaluation results. Example 2 As a polypropylene resin (Grand Polymer J
103), a foamed sheet was obtained by the method described in Example 1 except that the amount of the radical polymerization initiator was changed to 1.0 part by weight and the amount of the isoprene monomer was changed to 0.5 part by weight.

The obtained foam sheet was evaluated. The evaluation results are shown in Table 1. Comparative Example 1 Example 1 except that the amount of the isoprene monomer was 0 parts by weight.
The extruded foam sheet was formed by the method described, but the fusion to the cooling cylinder was large and a foam sheet could not be obtained. Comparative Example 2 A foamed sheet was obtained by the method described in Example 1, except that the amount of the radical polymerization initiator was changed to 0 parts by weight.

The obtained foam sheet was evaluated. Table 1 shows the evaluation results. Comparative Example 3 Polypropylene resin (manufactured by Montel, PF814)
100 parts by weight and blended oil (Koshigaya Chemical Industry Co., Ltd.)
, Super Ease) and 0.1 part by weight of sodium bicarbonate-citric acid (Serubon SC / K, manufactured by Eiwa Chemical Co., Ltd.) in a ribbon blender. 40mmφ, maximum screw effective length (L /
D) A 25.5 single-screw screw, the second-stage extruder is supplied to a first-stage twin-screw extruder of a tandem-type extruder comprising a single-screw extruder having a cylinder diameter of 50 mmφ, The heating temperature was 200 ° C., the screw rotation speed was 80 rpm, the discharge rate was 10 kg / hr, and isorich butane (iso / iso / n
= 85/15% by weight) at a ratio of 2.0 parts by weight (0.2 kg / hr) to 100 parts by weight of the melt-kneaded body,
The mixture was further melt-kneaded and continuously sent to the second-stage single-screw extruder. Next, in the second-stage single-screw extruder, the melt-kneaded body was cooled so that the temperature became 160 ° C., extruded at a screw rotation speed of 5 rpm, and attached to the tip of the second-stage single-screw extruder. The mixture was passed through an annular slit mold (diameter: 75 mmφ) adjusted to 160 ° C. to obtain an extruded tubular foam. The obtained tubular foam was stretched and cooled in a cooling cylinder (diameter: 150 mmφ) whose temperature was controlled at 25 ° C., and then cut and opened by a cutter to obtain a drawn foam sheet at a drawing speed of 1.5 m / min.

The obtained foam sheet was evaluated. Table 1 shows the evaluation results. Comparative Example 4 Polypropylene resin (F109 manufactured by Grand Polymer Co., Ltd.)
BA) 100 parts by weight of a radical polymerization initiator (Nippon Oil & Fats Co., Ltd., Perbutyl I) 0.5 part by weight was stirred and mixed with a ribbon blender. (TEX44XCT-38), 1.0 part by weight of isoprene was supplied from the middle of the extruder using a liquid addition pump, and the mixture was melt-kneaded in the twin-screw extruder.
By melt extrusion, pellets of the modified polypropylene resin composition 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.

Polypropylene resin (PF8 by Montell Corporation)
A foamed sheet was obtained by the method described in Comparative Example 1 except that the modified polypropylene resin obtained in place of 14) was used. The obtained foamed sheet was evaluated. Table 1 shows the evaluation results.

[0064]

[Table 1] The foam sheet in the example has a small sag amount and is excellent in heat moldability, whereas the foam sheet shown in Comparative Example 2 has a low closed cell ratio, a low number of cells in the thickness direction, and is inferior in workability. You can see that. In addition, in Comparative Examples 3 and 4, it can be seen that the moldability is inferior.

[0065]

The foamed sheet made of the modified polypropylene resin of the present invention has excellent moldability, and a good molded product can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) C08K 3/00 C08K 3/00 4J011 5/01 5/01 4J026 5/02 5/02 5/14 5 / 14 C08L 23/10 C08L 23/10 // B29C 44/00 B29C 67/22 B29K 23:00 105: 04 F term (reference) 4F071 AA15X AA20 AA20X AA21X AB02 AB17 AC02 AC03 AC08 AE01 AF06 AH03 AH05 AH11 BB06 BB07 BB09 BC01 BC11 4F074 AA24 AA25 AD01 AD08 BA32. AG20 AH17 AH55 AH56 AH58 KA01 KA11 KF01 KF03 KK01 KW23 4F212 AA11 AA46 AB02 AB03 AG20 AH17 AH55 AH56 AH58 UA10 UB02 UC06 UC08 UF01 UF06 UF21 UH21 4J002 AC035 AC065 AC08 BB035 BB065 BB075 BB085 BB095 BB121 BB141 BB145 BB151 BB155 BB175 BB235 BC035 BC065 BC075 BD045 BD055 BD105 BF025 BG045 BG105 BL015 BN155 BN165 BP015 BP021 DA008 DE018 EA016 EA018 EA028 EA049 EB028 EB029 EB068 EF049 EF079 EG019 EH079 EK017 EK037 EK047 EK057 EK077 EK087 EL039 EP019 ET009 FD010 FD020 FD030 FD050 FD070 FD090 FD100 FD130 FD140 FD170 FD20 FD32 FD328 GF00 GG01 GL00 GN00 4J011 AA05 AB02 BA04 BB03 DA02 DB19 GB06 PA64 PC02 PC13 SA76 WA07 XA02 4J026 AA13 DB02 GA01 AC02 DB33 GA07

Claims (6)

[Claims] 1. A mixture comprising a polypropylene resin, a radical polymerization initiator, and an isoprene monomer is supplied to an extruder, and the mixture is kneaded and melted at a temperature at which the radical polymerization initiator can be substantially decomposed. A kneaded body, a foaming agent is pressed into the melt-kneaded body, the melt-kneaded body into which the foaming agent has been pressed is cooled to a temperature suitable for foaming, and the melt-kneaded body is passed through a mold having an annular slit into a low-pressure region. The polypropylene resin is extruded into a tubular shape, and the tubular foam is stretched and cooled in a cooling tube, cut open, and then taken out into a sheet shape. A method for producing a modified polypropylene resin foam sheet. 2. A mixture comprising a polypropylene resin, a radical polymerization initiator, and an isoprene monomer is supplied to an extruder, and the mixture is kneaded and melted at a temperature at which the radical polymerization initiator can be substantially decomposed. A kneaded body, a foaming agent is pressed into the melt-kneaded body, the melt-kneaded body into which the foaming agent has been pressed is cooled to a temperature suitable for foaming, and the melt-kneaded body is passed through a mold having an annular slit into a low-pressure region. A foamed sheet obtained by extruding into a tubular shape, stretching and cooling the tubular foamed body in a cooling tube, cutting open the sheet, and taking it into a sheet. 3. The foamed sheet according to claim 1, wherein the resin composition is 18
The melt viscosity at 0 ° C. and a shear rate of 122 / sec is 800
The foamed sheet according to claim 2, wherein the pressure is 3,000 Pa · s. 4. The method according to claim 2, wherein the density is 0.5 to 0.05 g / cm ³ , the closed cell ratio is 60% or more, the thickness is 0.8 to 10.0 mm, and the number of cells in the thickness direction is 5 or more. Foam sheet. 5. A mixture comprising a polypropylene resin, a radical polymerization initiator, and an isoprene monomer is supplied to an extruder, and the mixture is kneaded and melted at a temperature at which the radical polymerization initiator can be substantially decomposed. A kneaded body, a foaming agent is pressed into the melt-kneaded body, the melt-kneaded body into which the foaming agent has been pressed is cooled to a temperature suitable for foaming, and the melt-kneaded body is passed through a mold having an annular slit into a low-pressure region. And expanded into a tubular shape, stretched and cooled in a cooling tube, cut open, and then taken out into a sheet to obtain a density of 0.5.
A molded article obtained by molding a foamed sheet having a thickness of 0.8 to 10.0 mm, a cell number of 5 or more in the thickness direction after heating in a heating furnace, and molding the foamed sheet having a closed cell rate of 60% or more, a thickness of 0.5 to 0.05 g / cm ³ or more. . 6. The resin composition constituting the foamed sheet is 18
The melt viscosity at 0 ° C. and a shear rate of 122 / sec is 800
The molded product according to claim 5, wherein the pressure is 3,000 Pa · s.