JP2000317969A - Production of polyolefinic resin composite foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composite foam having no irregularity in compression strength without cutting the vicinity of an edge part. SOLUTION: A polyolefinic resin is mixed with a modifying monomer in a molten state to be modified, and a heat decomposable chemical foaming agent is kneaded with the obtained moldified resin to obtain a foamable resin compsn. which is, in turn, molded into a sheet shape. A foaming suppressing sheet having strength capable of suppressing foaming in an in-plane direction when the obtained foamable resin sheet is heated and foamed is laminated to at least the single surface of the foamable resin sheet. When the obtained foamable composite sheet 5 is heated and foamed, foaming guides 4 are arranged along the edge parts of the sheet 5, and the foaming in the in-plane direction at the edge parts of the sheet 5 is obstructed by the guides to be guided in the thickness direction of the sheet 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a composite foam mainly composed of a polyolefin resin.

[0002]

2. Description of the Related Art In general, olefin resin foams such as polyethylene and polypropylene are widely used for various heat insulating materials, cushioning materials, floating materials, etc. because of their excellent lightness, heat insulating properties, flexibility and the like. However, since these materials have a lower compressive strength than polystyrene foams, they cannot be used, for example, for roof insulation of buildings or insulation for floors.

In order to solve this problem, for example, Japanese Patent Application Laid-Open
JP-A-42537 discloses that at least one side of a foamable polyolefin-based resin sheet containing a pyrolytic foaming agent has a strength capable of suppressing foaming in a two-dimensional direction (in-plane direction) when the sheet is heated and foamed. There has been proposed a composite foamable sheet obtained by laminating foam suppressing sheets having the same.

Since this composite foamable sheet is obtained by laminating a foam suppressing sheet as described above, when it is heated and foamed, it hardly foams in two-dimensional directions in the plane, but foams only in the thickness direction. I do. Therefore, as shown in FIG.
The cells (2) of the obtained foam (1) are arranged in a spindle shape having its major axis oriented in the thickness direction, that is, a rugby ball standing upright in the sheet thickness direction. Therefore, when the obtained foam receives a compressive force in the sheet thickness direction, a force is applied in the major axis direction of the spindle shape, so that the foam exhibits high strength in the thickness direction. In FIG. 1, (3) is a foam suppressing sheet.

[0005] However, the above prior art has the following problems. That is, since the foamable resin sheet has a foamed resin portion exposed on the side surface, especially when the foam has a thickness of 20 mm or more, the foamable resin portion far from the laminated foam suppressing sheet is particularly large. It is difficult to suppress the foaming in the two-dimensional direction (in-plane direction) at the center in the thickness direction, and at the free end in the in-plane direction, foaming occurs from the end face to a part of the in-plane direction. Therefore, at the edge of the foam, the cells are not arranged in order in the thickness direction, and the spindle-shaped cells fall down sideways. As a result, a high compressive strength characteristic of this kind of foam cannot be obtained in the vicinity of the edge, and when the foam is used for an application such as a floor insulating material, the edge should have a uniform compressive strength. The neighborhood must be cut.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method capable of obtaining a composite foam having no variation in compressive strength without cutting the vicinity of an edge in view of the above points. is there.

[0007]

According to the present invention, there is provided a method for producing a polyolefin resin composite foam according to the present invention, wherein the polyolefin resin is melt-mixed with a modifying monomer to modify the resin.
The obtained modified resin is kneaded with a thermal decomposition type chemical foaming agent, and the obtained foamable resin composition is shaped into a sheet. At least one side of the obtained foamable resin sheet is heated and foamed. At the time of laminating a foam suppressing sheet having a strength capable of suppressing foaming in the in-plane direction, and setting the foaming guide along the edge of the sheet when heating and foaming the obtained foamable composite sheet. In addition, this method is characterized in that the guide prevents foaming in the in-plane direction at the edge of the sheet and guides foaming in the thickness direction.

[0008] Throughout this specification, the term "in-plane direction" means any direction in the sheet surface of the foamable sheet, including the length direction and the width direction. In addition, the term “sheet” does not refer to a form in a strict sense based on thickness,
It includes a relatively thin film usually called a film and a relatively thick film usually called a plate material.

[0009] By heating the polyolefin resin foamable composite sheet obtained by the present invention and foaming by decomposing the foaming agent, a composite foam can be obtained.

The polyolefin constituting the main component of the polyolefin resin in the method of the present invention is a homopolymer of an olefinic monomer or a copolymer of a main component olefinic monomer and another monomer, and is not particularly limited. However, for example, low density polyethylene, high density polyethylene, polyethylene such as linear low density polyethylene,
Homo-type polypropylene, random-type polypropylene, polypropylene such as block-type polypropylene, polybutene, ethylene-propylene copolymer, ethylene-propylene-diene terpolymer, ethylene-butene copolymer, ethylene-vinyl acetate copolymer, Copolymers containing ethylene as a main component, such as ethylene- (meth) acrylate copolymers, are exemplified, and a combination of two or more of these may be used.

As the polyolefin constituting the main component of the polyolefin resin in the method of the present invention, one or a combination of two or more of the above-mentioned polyethylenes and polypropylenes is preferable.

The polyolefin resin refers to a resin composition in which the ratio of the polyolefin is 70 to 100% by weight. The resin other than the polyolefin constituting the polyolefin resin is not limited, and examples thereof include polystyrene and styrene elastomer. If the proportion of polyolefin in the polyolefin resin is less than 70% by weight, not only the characteristics of polyolefin such as light weight, chemical resistance, flexibility and elasticity cannot be exhibited, but also it is difficult to secure the melt viscosity required for foaming. This is not preferable because it may result in

The modifying monomer used in the method of the present invention is a compound having two or more functional groups capable of undergoing a radical reaction in a molecule. Examples of the functional group include an oxime group, a maleimide group, a vinyl group, an allyl group, and a (meth) acryl group. The modifying monomer is preferably a dioxime compound, a bismaleimide compound, divinylbenzene, an allyl polyfunctional monomer, or a (meth) acrylic polyfunctional monomer. Further, the modifying monomer may be a cyclic compound having two or more ketone groups or hydroxyl groups in a molecule, such as a quinone compound.

Among the modifying monomers used in the method of the present invention, first, a compound having two oxime groups in the molecule, that is, a dioxime compound, is an oxime group (formula I) or a hydrogen atom thereof represented by the following general formula. A structure in which an atom is replaced by another atomic group (mainly a hydrocarbon group) (Formula I
It is a compound having two I) in the molecule, and examples thereof include p-quinonedioxime (chemical formula III) and p, p-dibenzoylquinonedioxime (chemical formula IV). The dioxime compounds can be used in combination of two or more.

[0015]

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[0016]

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[0017]

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[0018]

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Among the modifying monomers used in the method of the present invention, examples of the bismaleimide compound having two maleimide structures (formula V) represented by the following general formula in a molecule include, for example, N, N'-p-phenylene Examples include bismaleimide (formula VI), N, N'-m-phenylenebismaleimide (formula VII), and diphenylmethane bismaleimide (formula VIII). Bismaleimide compounds can also be used in combination of two or more. Polymaleimides having two or more maleimide structures in the molecule (chemical formula IX) are also included in the category of bismaleimide compounds because they have the same effect.

[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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Among the modifying monomers used in the method of the present invention, a compound having two vinyl groups in the molecule, that is, a divinyl compound is, for example, divinylbenzene (compound X) represented by the following chemical formula, and the two vinyl groups are It may be in any of the ortho, meta and para positions.

[0026]

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Among the modifying monomers used in the method of the present invention, compounds having two or more allyl groups in the molecule, ie, allyl-based polyfunctional monomers include, for example, diallyl phthalate (formula XI), Lucyanurate (chemical formula XII), triallyl isocyanurate (chemical formula XIII), and diallyl chlorendate (chemical formula XIV) are exemplified. The allylic polyfunctional monomer may be used in combination of two or more.

[0028]

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[0029]

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[0030]

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[0031]

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Among the modifying monomers used in the method of the present invention, the compound having two or more (meth) acrylic groups in the molecule, that is, the (meth) acrylic polyfunctional monomer is, for example, a compound having two (meth) acryloyloxy groups. And compounds having from 4 to 4.

Examples of (meth) acrylic bifunctional monomers having two (meth) acryloyloxy groups include alkanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, and polyethylene glycol. Di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth)
Acrylate, dimethylol tricyclodecane di (meth) acrylate, ethylene glycol adduct of bisphenol A di (meth) acrylate, bisphenol A
And a propylene glycol adduct di (meth) acrylate.

The (meth) acrylic trifunctional monomers having three (meth) acryloyloxy groups include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, and trimethylolpropane ethylene oxide-added tri (meth) acrylate. A) acrylate, glycerin propylene oxide-added tri (meth) acrylate, and tris (meth) acryloyloxyethyl phosphate.

Examples of the (meth) acrylic tetrafunctional monomer having four (meth) acryloyloxy groups include pentaerythritol tetra (meth) acrylate and ditrimethylolpropanetetra (meth) acrylate.

Among the modifying monomers used in the method of the present invention, a typical example of a cyclic compound having two or more ketone groups or hydroxyl groups in a molecule is a quinone compound, and examples of the quinone compound include hydroquinone, p-benzoquinone, and tetrachlorobenzene. -P-benzoquinone is exemplified.

The amount of the modifying monomer may be appropriately selected according to the type of the monomer, but is generally 0.05 to 5 parts by weight, preferably 0.2 to 5 parts by weight, per 100 parts by weight of the polyolefin resin. ~ 2 parts by weight. If the amount of the modifying monomer is less than 0.05 part by weight, it is difficult to obtain a melt viscosity required for foaming. If the compounding amount exceeds 5 parts by weight, the degree of crosslinking is too high, and the extrudability is deteriorated (for example, a high load is applied and melt fracture occurs).
In addition, the foaming agent to be added later cannot be uniformly kneaded in the resin composition, and the gel fraction is unnecessarily increased too much, which may impair the recyclability. In addition, the foaming pressure at the time of heat foaming becomes too high later, and a foaming suppressing sheet for suppressing foaming in the in-plane direction may not be able to use a sheet having a low tensile strength.

In the method of the present invention, an organic peroxide may be used together with the modifying monomer. In particular, when a vinyl compound or an allyl compound is used as the modifying monomer, it is preferable to use an organic peroxide in combination with the vinyl compound or the allyl compound. The organic peroxide may be any one generally used in a graft reaction of polyolefin, and examples thereof include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, t-butylperoxyacetate, and t-butylperoxyacetate.
-Butylperoxybenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, di-t-butylperoxide,
2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3 and the like are preferably used alone or in combination of two or more.

In particular, dicumyl peroxide, 2,5-
One of dimethyl-2,5-di (t-butylperoxy) hexane, di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3 and the like Species or two or more species are more preferably used.

If the amount of the organic peroxide is too small, the conversion of the grafting reaction is insufficient, and if it is too large, the so-called β-cleavage of polypropylene occurs remarkably, and the molecular weight of the modified product is too low to deteriorate the physical properties. Alternatively, foaming failure may occur due to a decrease in viscosity. In consideration of these points, the amount of the organic peroxide to be used is preferably 0.001 to 0.5 part by weight, preferably 0.005 to 0.15 part by weight, based on 100 parts by weight of the polyolefin resin. More preferably, there is.

In order to obtain a modified resin, a polyolefin resin and a modifying monomer are melt-mixed under predetermined conditions and reacted by using a kneading apparatus such as a screw extruder or a kneader. The reaction temperature at this time is 170 ° C. or higher and the decomposition temperature of the polyolefin resin or lower, preferably 200 ° C. to 2 ° C.
50 ° C. If the melt mixing temperature is lower than 170 ° C., the denaturation is insufficient, and the expansion ratio of the finally obtained foam may not be sufficiently high. If it exceeds 250 ° C., the polyolefin resin is easily decomposed.

The apparatus used for the above-mentioned denaturation reaction may be a screw kneader or a melt kneading apparatus which can be generally used in plastic molding, and examples thereof include a kneader, a rotor and a continuous kneader. Among them, a screw extruder capable of continuous operation is preferable, and a single-screw extruder, a twin-screw extruder, a multi-screw extruder having three or more screws, and the like are all suitably used. As a single screw extruder, in addition to a general full flight screw, an extruder having a discontinuous flight screw, a pin barrel, a mixing head, and the like are also used. Further, as the twin screw extruder, a meshing co-rotating extruder, a meshing different direction rotating extruder, a non-meshing different direction rotating extruder and the like can be suitably used. Providing a vacuum vent at the latter stage of the extruder is effective for preventing volatiles from remaining in the resin composition.

When a screw extruder is used, the polyolefin resin is usually introduced into the extruder from a hopper, but it is also preferable to use a screw type feeder, a weight control type feeder or the like in order to increase the quantitativeness.

The modifying monomer may be fed into the extruder from the hopper simultaneously with the polyolefin resin. In particular, some of the divinylbenzene and allyl-based polyfunctional monomers are liquid at normal temperature and pressure. It is more preferable to supply the liquid from the liquid injection hole provided in the downstream part of the molten resin than from the position where the polyolefin resin is melted, since this can be uniformly dispersed in the molten resin. At this time, it is desirable that the liquid monomer be sent by a pressure-feeding pump such as a plunger pump.

When an organic peroxide is used in combination with the modifying monomer, the organic peroxide is preliminarily mixed with the same monomer and these are simultaneously charged, or the organic peroxide is separately charged before and after the monomer is charged. And the like.

The modified resin may be melt-blended with the same or different unmodified polyolefin resin. By using a blend of such a modified resin and an unmodified resin, the flowability of the foamable resin composition obtained is improved, and thereby, an extremely thin foamable raw material can be molded, and as a result, a thin sheet It is possible to manufacture a composite foam. In addition, the improvement of the fluidity of the foamable resin composition works favorably to form spindle-shaped cells, and as a result, it is possible to obtain a foam having higher compressive strength.

The unmodified polyolefin resin may be the same as described above in the definition of the polyolefin resin before modification of the modified resin.

The type of the unmodified polyolefin-based resin is determined by the moldability and appearance of the obtained foamable composite sheet, the adhesiveness to the foam-suppressing sheet, and the expansion ratio, mechanical properties, and thermal properties of the composite foam obtained therefrom. , Cell shape and the like. For example, if it is desired to improve the flowability of the raw foam, a resin having a low viscosity is used as the unmodified polyolefin resin. If a soft foam is desired, a low density polyolefin is used as the unmodified resin.

The ratio of the modified resin to the unmodified polyolefin resin is preferably 50 to 200 parts by weight, more preferably 70 to 200 parts by weight, based on 100 parts by weight of the modified resin.
130 parts by weight are blended. If the proportion of the unmodified polyolefin-based resin is too large, the melt tension required for foaming cannot be maintained, so that the foaming ratio may be reduced and a good foam may not be obtained.

The thermal decomposition type chemical blowing agent used in the present invention is not particularly limited as long as it generates a decomposition gas by heating. A typical example of a pyrolytic chemical blowing agent is
Azodicarbonamide, benzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, and 4,4-oxybis (benzenesulfonylhydrazide). These may be used alone or in combination of two or more. Among them, azodicarbonamide is particularly preferably used.

The thermal decomposition type chemical foaming agent is used in an appropriate amount in the range of 1 to 50 parts by weight, preferably 2 to 35 parts by weight, based on 100 parts by weight of the modified resin, according to a desired expansion ratio. .

In order to obtain a foamable resin composition by kneading a thermally decomposable chemical foaming agent into a modified resin obtained from a polyolefin resin and a modifying monomer in this manner, a melt-kneading apparatus for the reaction described above is used. And a different melt-kneading device for mixing the blowing agent (the structure may be the same as that of the melt-kneading device for the reaction), and the maximum temperature at which the blowing agent is not substantially decomposed To mix both. The mode of the melt kneading is as follows.

(A) In a batch or continuous melt-kneading apparatus for reaction, a polyolefin resin is melt-mixed with a modifying monomer and reacted, and the resulting modified resin is removed from the melt-kneading apparatus and solidified. After performing granulation, etc.
The resin composition is transferred to a batch-type or continuous kneading apparatus for mixing a foaming agent, into which a foaming agent is added, and both are melt-kneaded to obtain a foamable resin composition.

(B) In a batch-type melt-kneading apparatus for reaction, a polyolefin resin is melt-mixed with a modifying monomer and reacted, and the resulting modified resin is substantially decomposed in the kneading apparatus. After cooling to a temperature that does not cause decomposition or a temperature that does not decompose in a large amount, a foaming agent is added thereto, and both are melt-kneaded to obtain a foamable resin composition.

(C) In a screw extruder for reaction (continuous melt kneading apparatus), the polyolefin resin is melt-mixed with the modifying monomer at a temperature of 170 ° C. or more to react, and the resulting modified resin is foamed. The temperature is lowered to a temperature at which the agent does not substantially decompose or a large amount does not decompose,
Further, a foaming agent is introduced from a supply port provided in the middle of the screw extruder, and the two are melt-kneaded to obtain a foamable resin composition.

(D) In another mode of continuous operation, two screw extruders are connected, and the first is melt-mixed with a polyolefin-based resin and a modifying monomer to cause a reaction. After lowering the temperature of the resin in the same manner as described above, the same resin composition is transferred to a second unit, a foaming agent is added thereto, and the two are melt-kneaded to obtain a foamable resin composition.

The foamable resin composition obtained by kneading the mixture with a thermal decomposition type chemical foaming agent is shaped into a sheet. As a shaping method, in addition to extrusion molding, a method generally performed in plastic molding such as press molding, blow molding, calendaring molding, injection molding, or the like can be applied.

In particular, the foamable resin composition obtained according to the above-mentioned methods (a) and (b) is taken out from a batch-type kneading device for mixing a foaming agent, and is put into a screw extruder to continuously form a sheet. Method of shaping into a shape, or the above (a)
According to the methods (c) and (d), a method of directly shaping the foamable resin composition discharged from the screw extruder is preferable from the viewpoint of productivity.

The material constituting the foam suppressing sheet used in the method of the present invention can be freely selected from metals such as paper, cloth, wood, iron, etc., non-ferrous metals, plastics, glass and inorganic substances, and is not particularly limited. When the foam suppressing sheet is laminated and integrated with the foam sheet, it is desirable that the foam suppressing sheet exhibit a certain degree of adhesiveness with the foam sheet. Any material can be used as long as it can be bonded to the foamable sheet by appropriately using a pressure-sensitive adhesive or an adhesive by an anchor effect.

The foam-suppressing sheet has a strength capable of suppressing foaming in the in-plane direction when the foamable sheet is foamed by heating. If the strength of the foam-suppressing sheet is too low, the foam-suppressing sheet may be torn during foaming, and the foaming of the foamable sheet in the in-plane direction may not be sufficiently suppressed. Therefore, as the foam suppressing sheet for suppressing the in-plane foaming, for example, when the expansion ratio is 10, a sheet having a tensile strength of 0.1 kgf / cm or more is preferable.

The foam-suppressing sheet preferably used in the method of the present invention includes glass cloth, cold gauze, woven or nonwoven fabric, needle punched nonwoven fabric, paper and the like. The glass cloth refers to a surface mat obtained by forming glass fibers and a glass roving woven. The cold gauze, the nonwoven fabric, and the needle punch are mainly made of synthetic fibers such as polyester and nylon. The woven fabric may be made of general natural fibers or synthetic fibers. Note that the surface mat may include a binder for binding the short glass fibers to each other. The binder is not particularly limited as long as the tensile strength of the foam-suppressing sheet satisfies the above range, and examples thereof include thermoplastic resins such as polyvinyl alcohol, saturated polyester, and acrylic resins, epoxy resins, and unsaturated polyesters. Thermosetting resin. Examples of the organic fibers constituting the woven or nonwoven fabric include polyester fibers, cotton, acrylic fibers, nylon fibers, carbon fibers, and aramid fibers. By using these foam suppressing sheets, it is possible to obtain a polyolefin resin composite foam having a light weight and a high compressive strength. Also,
By using a foam-suppressing sheet having appropriate strength, secondary shaping can be performed by reheating the foam to a temperature equal to or higher than the melting point of the polyolefin-based resin. Therefore, the obtained composite foam can be suitably used as a molded ceiling material for automobiles and a core material for interior panels and the like.

The foam suppressing sheet used in the method of the present invention may be a metal sheet, for example, an iron sheet or a non-ferrous metal sheet such as aluminum, titanium and copper. The iron sheet includes a molten zinc steel sheet, a molten zinc aluminum alloy steel sheet, a stainless steel sheet, and the like. As such a metal foaming suppression sheet, a rolled thin sheet having a thickness of 0.01 mm to 2 mm is particularly preferably used. In this case, these metals may be arbitrarily plated, may be coated with an organic paint or an inorganic paint, or may be coated with an adhesive. When using these metal foam-suppressing sheets, the resulting polyolefin-based resin composite foam can be a lightweight metal composite plate. Compared to a metal plate with a thickness of 1 to 5 mm or a metal composite plate in which a polyethylene layer is arranged as an intermediate layer, it is possible to further reduce the weight and cost without causing extreme shortage of strength in practical use. It has the merit that can be achieved. Further, since this composite foam is produced by foaming a foamable composite sheet, the surface smoothness is extremely excellent as compared with a metal composite plate in which a metal foam suppression sheet is later attached to the foam.

The method of laminating the foam-suppressing sheet on at least one side of the foamable sheet is not particularly limited. For example, (a) a method of attaching the sheet-like material to a foamed sheet once cooled and solidified while heating the sheet-like material (B) a method in which the foamable sheet is heated until it is in a molten state, and this is heat-sealed to the foamable sheet, and (c) a method in which the foamable sheet is bonded to the foamable sheet with an adhesive. Can be

In order to ensure the thickness accuracy of the foamable composite sheet, the method (a) or (c) is preferable. In the heat fusion of the method (b), for example, a foam-suppressing sheet is lightly laminated on at least one side of a foamed sheet in a molten state immediately after being extruded from a T-die, and these are placed between opposed cooling rolls. A method is preferable in which the two are passed and the two are integrated by the pressing force of the roll.

As described above, when the foamable sheet and the foam-suppressing sheet are laminated and integrated, when the foamable sheet and the foam-suppressing sheet are peeled off at the interface between them, a high rate of material destruction occurs. It means a state where both are fixed to the extent that they occur.

The foamable composite sheet thus obtained can be foamed to a desired expansion ratio under normal pressure or constant pressure by heating it under an appropriate temperature condition.
The heating is usually performed in a temperature range from the decomposition temperature of the thermal decomposition type chemical foaming agent to the decomposition temperature + 100 ° C. Particularly, as a continuous foaming apparatus, in addition to a take-up foaming machine that foams while taking out a foam at an outlet side of a heating furnace, a belt-type foaming machine, a vertical or horizontal foaming furnace, a hot-air constant temperature bath, or an oil bath, metal A hot bath such as a bath or a salt bath is used.

The foaming guide used in the method of the present invention means that when the foamable composite sheet is heated and foamed, the foaming guide is set along the edge of the sheet, and the guide is used for the edge of the sheet. It is used for the purpose of preventing foaming in the in-plane direction at the portion and guiding the foaming in the thickness direction.

Here, the edge of the sheet means, in the case of batch foaming, all side edges of the foamable composite sheet, for example,
Refers to both sides and both ends of a rectangular foam composite sheet when viewed in a plane. In the case of continuous foaming, the foam composite sheet has no edges in the flow direction. Refers to both sides of the seat. It is preferred that the foaming guide be installed at all edges.

The foam guide has a foam preventing surface along the edge of the foam composite sheet and parallel to the thickness direction. If the foam prevention surface is not parallel to the thickness direction, foaming in the in-plane direction of the foamable composite sheet cannot be uniformly suppressed, and the spindle-shaped cells are inclined with respect to the thickness direction, and the compressive strength varies. The height of the foam preventing surface of the foam guide is preferably larger than the final thickness of the obtained foam. If the height of the foam preventing surface is smaller than the final thickness of the foam, foaming in the in-plane direction of the edge of the foamable composite sheet cannot be sufficiently suppressed until the final stage of foaming.

It is necessary that the material of the foaming guide does not change the above-described configuration and shape of the foaming guide due to the foaming pressure. If the configuration and shape of the foaming guide change, foaming in the in-plane direction of the edge of the foamable composite sheet cannot be sufficiently suppressed.

It is necessary that the foam preventing surface of the foaming guide does not hinder foaming in the thickness direction, that is, it has a small frictional resistance against foaming in the thickness direction. If the friction resistance of the foam preventing surface is large, this inhibits foaming of the edge in the thickness direction, and a spindle-shaped cell cannot be obtained. In order to reduce the frictional resistance, it is also preferable to apply a Teflon process to the foam preventing surface of the foaming guide, apply a lubricant to the foam preventing surface, or flow the lubricant.

The foaming guide is set along the edge of the foamable composite sheet. Along the edge of the foamable composite sheet means a state in which the edge is located opposite to the edge at a predetermined interval or in contact with the edge. In the former case, the interval is preferably within 10 mm, more preferably within 5 mm from the side surface or end surface of the foamable composite sheet. This interval is 10
If it exceeds mm, foaming in the in-plane direction of the edge of the foamable composite sheet cannot be sufficiently suppressed.

Next, examples of installation positions of the foaming guide will be described, but these examples are not limited. It is possible to install a foaming guide so as to meet the above conditions.

1) Example of batch-type foaming As shown in FIG. 2, in the case of batch-type foaming, foaming may occur in the in-plane direction on both side surfaces and all of the both side surfaces of the expandable composite sheet having a rectangular shape in plan view. There is. Therefore, a foaming guide (4) in the form of a bottomed square tube having a foam-inhibiting surface (6) on all sides is prepared, and the foamable composite sheet (5) is placed in the guide. To the foaming prevention surfaces (6) of the foaming guide (4) in opposition to each other.

2) Example of continuous foaming As shown in FIG. 3, in a continuous foaming line flowing in one direction, since the foamable composite sheet has no edge in the flow direction, it is provided on both sides of the conveyor belt (7). A belt-like foaming guide (8) is provided in conjunction with the belt. Both sides of the foamable composite sheet (5) on the conveyor belt (7) are brought into contact with and against the foam prevention surface (9) of the foaming guide (8). The transport belt (7) and the belt-like foaming guide (8) are preferably made of a Teflon belt.

[0076]

In the manufacturing method according to the present invention, when the foamable composite sheet is heated and foamed, the foaming guide is set along the edge of the sheet. Thereby, the edge of the foamable composite sheet becomes a fixed end, and the foaming in the in-plane direction can be sufficiently prevented to guide the foaming in the thickness direction. As a result,
The spindle-shaped cells are aligned in the thickness direction over the entire area of the foam, and the compressive strength is uniform.

[0077]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described more specifically with reference to embodiments.

Example 1 i) Production of foamable resin composition (1) Preparation of modified polyolefin resin As a screw extruder for reaction, a BT40 (manufactured by Plastic Engineering Laboratory) co-rotating twin screw extruder was used. Was. It has a self-wiping double-start screw with an L / D of 35 and a D of 39 mm. The cylinder barrel is composed of first to sixth barrels from upstream to downstream of the extruder. The die is a three-hole strand die, and a vacuum vent is provided in the fourth barrel to collect volatile components.

The operating conditions are as follows.

Cylinder barrel set temperature: 1st barrel; 180 ° C 2nd to 6th barrel; 220 ° C die; 220 ° C Screw rotation speed: 150 rpm

First, a polyolefin-based resin is charged from the rear end hopper into the modifying screw extruder having the above structure, and a mixture of the modifying monomer and the organic peroxide is injected into the extruder from the third barrel, and these are melted. This was mixed to obtain a modified resin. At this time, the volatile components generated in the extruder were evacuated by a vacuum vent.

The polyolefin resin is a polypropylene random copolymer (“EX6” manufactured by Nippon Polychem, MI;
1.8, density; 0.9 g / cm ³ ), and the supply amount was 10 kg / h.

The modifying monomer was divinylbenzene, and the supply amount was 0.5 parts by weight based on 100 parts by weight of the polyolefin resin.

The organic peroxides include 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-
3, and the supply amount was 0.1 part by weight based on 100 parts by weight of the polyolefin resin.

The modified resin obtained by melt-mixing the polyolefin resin, the modifying monomer and the organic peroxide was discharged from a strand die, cooled with water, and cut with a pelletizer to obtain pellets of the modified resin.

(2) Preparation of foamable resin composition The screw extruder for kneading the foaming agent is a TEX-44 type (manufactured by Nippon Steel Works) co-rotating twin screw extruder,
It is equipped with a self-wiping double-start screw and its L
/ D is 45.5 and D is 47 mm. The cylinder barrel comprises first to twelfth barrels from upstream to downstream of the extruder, and the forming die is a 7-hole strand die.

The temperature setting categories are as follows. 1st barrel is always cooled 1st zone; 2nd to 4th barrel 2nd zone; 5th to 8th barrel 3rd zone; 9th to 12th barrel 4th zone; Die and adapter part

A side feeder is installed in the sixth barrel to supply the foaming agent, and the eleventh barrel is used to collect volatile components.
A vacuum vent is installed in the barrel.

The operating conditions are as follows.

[0090]

The modified resin obtained as described above and a homo-type polypropylene (“FY” manufactured by Nippon Polychem Co., Ltd.)
4 ", MI; 5.0, density; 0.9 g / cm ³ ) were supplied to the blowing agent kneading screw extruder at a supply rate of 10 kg / h. Further, a blowing agent (azodicarbonamide (ADCA)) was supplied to the extruder at a supply rate of 1.5 kg / h from a side feeder.

The foamable resin composition obtained by kneading the modified resin and the foaming agent was extruded from a T-die to obtain a foamable sheet having a width of 350 mm and a thickness of 3.1 mm.

(3) Preparation of Composite Sheet A nonwoven fabric made of polyethylene terephthalate (manufactured by Toyobo Co., Ltd., on both sides of the foamable sheet obtained as described above)
"Spunbond Ecoulet 6301A", weighing 30g
/ M ² , tensile strength: 1.6 kg / cm in height, 1.2 k in width
g / cm) and using a press molding machine at 180 ° C.
It was shaped at 200 kgf / cm ² to obtain a foamable composite sheet having a thickness of 1 mm. The edge was removed from the obtained foamable composite sheet to obtain a square sample having a side of 300 mm.

(4) Foaming As shown in FIG. 2, a foaming guide (4) made of stainless steel (SUS) and having a bottomed cylindrical shape is prepared, and the inner surface on each side thereof, that is, the foam preventing surface (6) Was coated with a fluororesin release agent. Foamable composite sheet inside foaming guide (4)
(5) was accommodated, and both side surfaces and both end surfaces of the expandable composite sheet were brought into contact with the four foam preventing surfaces (6) of the foaming guide (4) so as to face each other. Then, add two foaming guides (4)
It was placed in an oven at 30 ° C. and heated for about 5 minutes to foam the foamable composite sheet to obtain a composite foam.

Comparative Example 1 The foamable composite sheet obtained in the preparation step (3) of the composite sheet was placed in a stainless steel vat lined with talc and placed in an oven to foam the sheet. Except for the above, a composite foam was obtained in the same manner as in Example 1. The composite foam had to be cut about 2 cm from the edge. In addition, when the conventional manufacturing method is used, a heat curing process and a drying process are added, and the process becomes complicated.

Performance Evaluation The composite foams obtained in the above Examples and Comparative Examples were evaluated for the following items. The evaluation results are summarized in Table 1.

[0097] Expansion ratio: After the foaming-suppressing sheet was scraped off from the composite foam with a cutter, the expansion ratio of the foam was measured in accordance with JIS K6767.

Compressive modulus, 5% compressive strength: The composite foam was cut into 5 cm squares at the positions shown in FIG. 4 (three samples obtained were named A, B, and C from the ends). J
According to IS K 7220, the sample was 10 mm / m
The compression was performed at a speed of "in", the compression elastic modulus was calculated from the curve in the elastic deformation region, and the 5% compression strength was determined.

Cell shape (major axis length / minor axis length): The composite foam was cut in the thickness direction, and the spindle-shaped foam cells were visually observed and evaluated according to the following criteria.

：: Spindle-shaped cells are arranged substantially parallel to the thickness direction.

△: Spindle-shaped cells are arranged at an angle of about 5 to 10 ° with respect to the thickness direction.

×: Spindle-shaped cells are arranged at an angle of 10 ° or more with respect to the thickness direction.

[Table 1]

[0103]

According to the polyolefin resin composite foam obtained by the production method of the present invention, the foaming at the edge is limited only in the thickness direction by the foaming guide which is a feature of the present invention. Until then, spindle-shaped cells are neatly arranged parallel to the thickness direction. For this reason, the cells were usually arranged at an angle, and the edges where the compressive strength was impaired were cut off to obtain only parts having uniform physical properties.However, in the manufacturing method according to the present invention, uniform compression was performed up to the edges. Strength is exhibited, waste of materials and raw materials can be prevented, and efficient production of composite foams becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a composite foam.

FIG. 2A is a schematic view of a batch type foaming guide, and FIG. 2B is a vertical sectional view thereof.

FIG. 3 (a) is a schematic view of a continuous foaming guide, FIG.
(b) is a vertical sectional view thereof.

FIG. 4 is a schematic view of a sample acquisition position of a composite foam.

[Explanation of symbols]

 1: composite foam 2: cell 3: foam suppression sheet 4, 8: foam guide 5: foam composite sheet 6, 9: foam prevention surface 7: transport belt

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 23:00 105: 04 B29L 9:00 F term (Reference) 4F074 AA28 BA13 BA16 BA18 BA19 CA29 CC04Y CC22X CC62 DA32 4F212 AA03 AB02 AB03 AD05 AD16 AG03 AG20 AH48 AK11 UA09 UB01 UE27 UG05 UK09 UN02 UN05 4J002 BB201 EQ016 ES006 EV286 FD326 GL00

Claims (1)

[Claims] 1. A polyolefin-based resin is melt-mixed with a modifying monomer to modify the resin, and the resulting modified resin is kneaded with a thermal decomposition type chemical foaming agent. The foamed resin sheet obtained is laminated on at least one side of the obtained foamable resin sheet, and a foaming suppression sheet having a strength capable of suppressing foaming in an in-plane direction when the sheet is heated and foamed. When the composite sheet is heated and foamed, a foaming guide is set along the edge of the sheet, and the guide prevents foaming in the in-plane direction at the edge of the sheet, thereby suppressing foaming in the thickness direction. A method for producing a polyolefin-based resin composite foam, comprising: