JP2002080609A - Process for producing modified polypropylene, and foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a modified polypropylene by which a modified polypropylene excellent in flowability and having a high melt tension can be obtained, and to provide a process for producing a modified polypropylene by which a modified polypropylene having a beautiful appearance and excellent in heat resistance can be obtained. SOLUTION: The process for producing a modified polypropylene resin composition comprises melting and kneading at 160 to 250 deg.C a polypropylene resin (A) with a peroxide (B) capable of crosslinking a polypropylene, and then melting and kneading at 160 to 250 deg.C the obtained kneaded material with a peroxide (C) capable of decomposing a polypropylene.

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 modified polypropylene and a foam, and more particularly, to a modified method in which polypropylene, a polypropylene crosslinked peroxide, and a polypropylene decomposable peroxide are melt-kneaded in a specific order. The present invention relates to a method for producing polypropylene and a foam obtained from the modified polypropylene produced by this method.

[0002]

BACKGROUND OF THE INVENTION Foams made of thermoplastic resin are:
Generally, since it is lightweight and has good heat insulating properties and good buffering properties against external stress, it is widely used as a heat insulating material, a buffer material, a core material, a food container and the like. Above all, foams made of polypropylene have good chemical resistance, impact resistance and heat resistance, and are excellent in food hygiene, so that their use as trays for fresh foods has been studied.

However, since polypropylene is a crystalline resin, the viscosity and melt tension at the time of melting are low, and when foaming polypropylene, there is a problem that cells are easily broken at the time of foaming. For this reason, it was difficult to foam polypropylene to obtain a low-density foam excellent in appearance and excellent in secondary workability. As a method for improving the foaming property of polypropylene, for example, a method of adding a foaming agent and a crosslinking assistant to polypropylene to produce a foam while crosslinking the molecules thereof is disclosed in, for example, Japanese Patent Publication No. 45-4.
No. 0420 has been proposed. However, even with this method, the melt tension of the polypropylene is insufficiently improved, and a cross-linking aid that does not cross-link the polypropylene remains, resulting in a strong odor, which is not suitable for food packaging.

As a method for improving the foaming property of polypropylene, a method of blending polypropylene with polypropylene and foaming the same is disclosed in, for example, JP-B-44-25.
No. 74, for example. However, the effect of improving the melt tension of polypropylene by this method is small, and a foam having excellent secondary workability cannot be obtained. By the way, WO 99/27007 describes using a peroxydicarbonate compound as a radical polymerization initiator.

[0005] However, this publication proposes a modified blend of several levels of one kind of propylene homopolymer, one kind of polypropylene block copolymer, one kind of polypropylene random copolymer and several kinds of peroxydicarbonate compounds. There is no suggestion on what kind of formulation should be adopted to obtain a resin having characteristics suitable for foam molding, only by introducing a high-quality polypropylene resin.

As a result of investigations by the present inventors, the modified polypropylene obtained by reacting polypropylene with a peroxydicarbonate compound has an increased melt viscosity.
Often, the strands are cut during granulation to make granulation difficult, and when formed into a sheet, the surface may be rough and the appearance may be poor.

[0007]

An object of the present invention is to provide a method for producing a modified polypropylene having improved foamability and a modified polypropylene produced by this method. It is intended to provide a foam. Further, the present invention provides a method for producing a modified polypropylene which is excellent in food hygiene and can be used as a foamed polypropylene suitable for food trays and the like, and a foam obtained from the modified polypropylene produced by this method. It is an object.

Further, the present invention provides a method for producing a modified polypropylene which is excellent in heat resistance, has a high expansion ratio, has excellent secondary workability, has a low density and is suitable for producing a foam having a beautiful appearance. It is an object of the present invention to provide a foam obtained from the modified polypropylene produced by the above-mentioned method.

[0009]

SUMMARY OF THE INVENTION A method for producing a modified polypropylene according to the present invention comprises melting and kneading a polypropylene (A) and a polypropylene crosslinked peroxide (B) at 160 to 250 ° C., and then mixing the obtained kneaded product with a polypropylene decomposed type. It is characterized by melting and kneading peroxide (C) at 160 to 250 ° C.

In the present invention, the polypropylene crosslinked peroxide (B) is preferably peroxydicarbonate, and the peroxydicarbonate is bis (4-t-butylcyclohexyl) peroxydicarbonate or dicetyl peroxydicarbonate. It is preferred that In the present invention, the polypropylene-decomposed peroxide (C) is preferably a dialkyl peroxide, and the dialkyl peroxide is preferably 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane.

The foam according to the present invention is characterized by being obtained by foaming the modified polypropylene obtained by the above method.

[0012]

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, a method for producing a modified polypropylene and a foam according to the present invention will be specifically described. In the method for producing a modified polypropylene according to the present invention, polypropylene (A) and polypropylene crosslinked peroxide (B) are melt-kneaded, and then melt-kneaded with polypropylene decomposable peroxide (C). First, each component used in the present invention will be described.

(A) Polypropylene The polypropylene (A) (hereinafter sometimes referred to as “raw material polypropylene”) used in the present invention comprises propylene homopolymer or propylene and α having 2 to 20 carbon atoms excluding propylene. -A copolymer with at least one α-olefin selected from olefins.

Here, C 2 -C 2 except propylene
As α-olefins of 0, ethylene, 1-butene, 1-
Pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene and the like, and ethylene or carbon atom Alpha-olefins having 4 to 10 numbers are preferred.

[0015] These α-olefins may form a random copolymer with propylene or a block copolymer. The constituent units derived from these α-olefins may be contained in the polypropylene (A) in a proportion of 5% or less, preferably 2% or less. Melt flow rate of polypropylene (A) (ASTM
D 1238, 230 ° C., load 2.16 kg) is usually 0.4 to 15 g / 10 min, preferably 1.0 to 10 g / 10 min.
In the range of minutes.

If necessary, a resin or rubber other than the polypropylene (A) may be added to the polypropylene (A) as long as the effects of the present invention are not impaired. Examples of the other resin or rubber include polyethylene;
Poly-α-olefins such as poly-1-butene, polyisobutene, poly-1-pentene and polymethyl-1-pentene; ethylene / propylene copolymers having less than 75% by weight of propylene, ethylene / 1-butene copolymers A copolymer of two α-olefins selected from α-olefins having 2 to 20 carbon atoms, such as a propylene / 1-butene copolymer having a propylene content of less than 75% by weight; a propylene content of 75% by weight % Ethylene / propylene / 5-ethylidene
Copolymer of two kinds of α-olefins selected from α-olefins having 2 to 20 carbon atoms such as 2-norbornene copolymer and diene monomer; ethylene / vinyl chloride copolymer, ethylene / Vinylidene chloride copolymer, ethylene / acrylonitrile copolymer, ethylene / methacrylonitrile copolymer, ethylene / vinyl acetate copolymer, ethylene / acrylamide copolymer, ethylene / methacrylamide copolymer, ethylene / acrylic acid copolymer Polymer, ethylene / methacrylic acid copolymer, ethylene / maleic acid copolymer, ethylene / ethyl acrylate copolymer, ethylene /
Butyl acrylate copolymer, ethylene / methyl methacrylate copolymer, ethylene / maleic anhydride copolymer, ethylene / metal acrylate copolymer, ethylene / metal methacrylate copolymer, ethylene / styrene copolymer Coalescing,
Copolymer of one kind of α-olefin selected from α-olefins having 2 to 20 carbon atoms such as ethylene / methylstyrene copolymer and ethylene / divinylbenzene copolymer with a vinyl monomer; polyisobutene, polybutadiene ,
Polydiene copolymers such as polyisoprene; vinyl monomers such as styrene / butadiene random copolymer / diene monomer random copolymers; vinyl monomers such as styrene / butadiene / styrene block copolymer / Diene monomer / vinyl monomer block copolymer; hydrogenation (vinyl monomer / diene monomer random copolymer) such as hydrogenation (styrene / butadiene random copolymer); hydrogenation ( Hydrogenation (vinyl monomer / diene-based monomer / vinyl monomer block copolymer) such as styrene / butadiene / styrene block copolymer; acrylonitrile / butadiene / styrene copolymer, methyl methacrylate / butadiene / Vinyl monomers such as styrene copolymers / diene monomers / vinyl monomer graft copolymers;
Vinyl polymers such as polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyvinyl acetate, polyethyl acrylate, polybutyl acrylate, and polymethyl methacrylate; vinyl chloride / acrylonitrile copolymer, vinyl chloride / vinyl acetate copolymer And vinyl copolymers such as acrylonitrile / styrene copolymer and methyl methacrylate / styrene copolymer.

The amount of the other resin or rubber to be added to the polypropylene (A) varies depending on the type of the other resin or rubber, and may be within the range that does not impair the effects of the present invention as described above. Usually, it is preferably about 25% by weight or less. Furthermore, an antioxidant, an ultraviolet absorber,
Additives such as metal soaps, stabilizers such as hydrochloric acid absorbents, nucleating agents, lubricants, plasticizers, fillers, reinforcing agents, pigments, dyes, flame retardants, and antistatic agents within a range that does not impair the effects of the present invention. It may be added.

(B) Polypropylene Cross-Linked Peroxide The polypropylene cross-linked peroxide (B) used in the present invention is a peroxide such that when melt-processed with polypropylene, the intrinsic viscosity of polypropylene increases and the apparent molecular weight increases, An example is peroxydicarbonate.

The peroxycarbonate has the general formula R¹-
OC (O) OOC (O) OR^Two With a compound represented by
is there. Where R¹And R^TwoAre the same but different
May be, CH_Three, 2-i-C_ThreeH₇OC₆H_Four, C_TwoH_FiveCH
(CH_Three), 4-CH_Three-C₆H_Four, Cl_ThreeCC (CH_Three)_Two, C
₇H_Fifteen, C-C₆H₁₁CH_Two, 3-t-C_FourH₉-C₆H_Five, Cl_ThreeS
i (CH_Two)_Three, C₆H_Five, CH_ThreeCH (OCH_Three) CH_TwoC
H_Two, C₆H_FiveOCH_TwoCH_Two, C₆H_FiveCH_Two, Z-C₈H₁₇C
H = CH (CH_Two)₈, 2-CH_Three-C₆H_Four, (CH_Three)_TwoCH
CH_TwoCH (CH_Three), 3,4-di-CH_Three-C₆H_Three, Cl_ThreeC,
CHCH (Cl), ClCH_Two, [C_TwoH_FiveOC (O)]_Two
CH (CH_Three), 3,5-di-CH_Three-C₆H_Three, C₈H₁₇, C_TwoH
_Five, C₁₈H ₃₇, 2-oxo-1,3-dioxane-4-CH_Two, C_Two
H_FiveCH (Cl) CH_Two, 4-CH_ThreeOC₆H_Four, I-C_FourH₉,
CH_ThreeSO_TwoCH_TwoCH_Two, C₁₂H_{twenty five}, C₆H_FiveCH (Cl)
CH _Two, H_TwoC = CHCH_Two, 2-Clc-C₆H_Ten, H_TwoC =
C (CH_Three) CH_Two, C-CH₆H ₁₁, ClCH_TwoCH_Two,Four-
[C₆H_Five-N = N] -C₆H_FourCH_Two, Stearyl, 1-naph
Chill, 4-t-C_FourH₉-C₆H_Ten, 2,4,5-tri-Cl-C₆H_Two,
C₁₄H₂₉, 9-fluorenyl, 4-NO_Two-C₆H_FourCH_Two, 2-i
-C_ThreeH₇-C₆H_Four, CH_ThreeOCH_TwoCH_Two, H_TwoC = C (CH
_Three), 3-CH_Three-C₆H_Four, BrCH_TwoCH_Two, 3-CH_Three-5-i-
C_ThreeH₇-C₆H_Three, Br_ThreeCCH_Two, C_TwoH_FiveOCH_TwoCH_Two,
HC_Two= CH, i-C_ThreeH₇, 2-C_TwoH_FiveCH (CH_Three) -C₆H
_Four, Cl_ThreeCCH_Two, C_FiveH₁₁, C-C₁₂H_{twenty three}, 4-t-C_FourH₉-
C₆H_Four, C₆H₁₃, C_ThreeH₇, C₆H₁₃CH (CH_Three), C
H_ThreeOC (CH_Three)_TwoCH_TwoCH_Two, C_ThreeH ₇OCH_TwoCH_Two,
CH_ThreeOCH_TwoCH (CH_Three), 2-i-C_ThreeH₇-5-CH_Three-c-C
₆H₉, C_FourH₉OCH_TwoCH_Two, T-C_FourH₉, (CH_Three)_ThreeCC
H_TwoAnd the like.

Here, i means iso, t means tertiary, z means cis, and c means cyclic. Preferred compounds among these compounds include bis (4-t-butylcyclohexyl) peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, diisopropylperoxydicarbonate, di-n-butylperoxydicarbonate, (2-ethylhexyl) peroxydicarbonate and the like.

Of these, bis (4-t-butylcyclohexyl) peroxydicarbonate and dicetyl peroxydicarbonate are particularly preferred because of their excellent crosslinking effect. These polypropylene crosslinked peroxides (B) can be used alone or in combination of two or more.

The amount of the polypropylene crosslinked peroxide (B) to be added is preferably in the range of 0.3 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, based on 100 parts by weight of the polypropylene (A). Is more preferably within the range. (C) Polypropylene-decomposed peroxide The polypropylene-decomposed peroxide (C) used in the present invention is obtained by melt-treating with polypropylene (A).
A peroxide in which the intrinsic viscosity of the polypropylene (A) decreases and the molecular weight decreases.

Polypropylene decomposable peroxide (C)
Examples thereof include ketone peroxides such as methyl ethyl ketone peroxide and methyl acetoacetate peroxide; 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, Peroxyketals such as n-butyl-4,4-bis (t-butylperoxy) valerate and 2,2-bis (t-butylperoxy) butane; permethane hydroperoxide, 1,1,3,3-tetramethylbutyl Hydroperoxides such as hydroperoxide, diisopropylbenzene hydroperoxide and cumene hydroperoxide; dicumyl peroxide, 2,5-dimethyl-
2,5-di (t-butylperoxy) hexane, α, α′-bis (t-butylperoxy m-isopropyl) benzene, t-butylcumyl peroxide, di-t-butylperoxide,
2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-
Dialkyl peroxides such as 3; diacyl peroxides such as benzoyl peroxide; di (3-methyl-3-methoxybutyl) peroxydicarboneropyr) benzene, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5- Dimethyl-2,5-di (t-butylperoxy)
Dialkyl peroxides such as hexyne-3; diacyl peroxides such as benzoyl peroxide; t-butylperoxyoctate, t-butylperoxysobutyrate, t-butylperoxylaurate, t-butylperoxy 3,5,5-trimethylhexano Peroxy such as ethate, t-butylperoxysopropyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate, t-butylperoxybenzoate, di-t-butylperoxysophthalate Esters and the like.

Among these polypropylene decomposable peroxides (C), dialkyl peroxides are preferred, and 2,5-dimethyl-2,5-di (t-butylperoxy) hexane is particularly preferred because of its low peroxide decomposition temperature, It is preferable because it has little odor. These polypropylene decomposable peroxides (C) can be used alone or in combination of two or more.

The amount of the polypropylene-decomposed peroxide (C) to be added is preferably in the range of 0.001 to 0.5 part by weight, and more preferably 0.005 to 0 part by weight, per 100 parts by weight of the polypropylene (A). More preferably, it is in the range of 0.2 parts by weight. When the amount of the polypropylene-decomposed peroxide (C) is within the above range, a sufficient effect of modifying the fluidity of the modified polypropylene by the polypropylene-decomposed peroxide (C) is obtained, and the MFR of the modified polypropylene is increased. The modified polypropylene with reduced melt tension does not impair the cross-linking and foaming performance of the modified polypropylene.

In the present invention, the above-mentioned polypropylene (A) and the polypropylene-crosslinked peroxide (B) are melt-kneaded, and then the obtained kneaded product and the polypropylene-decomposed peroxide (C) are melt-kneaded. A vinyl monomer may be allowed to coexist during such melt kneading. Examples of the vinyl monomer used as necessary in the present invention include, for example, vinyl chloride, vinylidene chloride, styrene, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, and maleic anhydride. Acid, metal acrylate,
Acrylates such as metal methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, glycyl acrylate; methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacryl And methacrylic esters such as 2-ethylhexyl acid, stearyl methacrylate, and glycyl methacrylate.

[0027] In the manufacturing method of the present invention, first, the polypropylene (A), a polypropylene crosslinked peroxide (B) and other additives optionally used, a ribbon blender, a tumbler blender and mixed like a Henschel blender. The mixed polypropylene (A), the polypropylene crosslinked peroxide (B) and other optional additives are then melt kneaded to obtain a kneaded product (partially crosslinked polypropylene).

Examples of the melt kneading apparatus include a kneader such as a co-kneader, a Banbury mixer, a Brabender, a single-screw extruder, a twin-screw extruder, a horizontal shaking machine such as a twin-screw renewer, and a twin-screw multi-disc device. A vertical stirrer such as a double helical ribbon stirrer can be employed. Among them, a twin-screw extruder is particularly preferable because it can sufficiently knead and excel in productivity. In addition, the melt-kneading may be repeated a plurality of times in order to sufficiently and uniformly mix the respective materials.

The heating temperature during melt-kneading is from 160 to 250
° C, preferably 170-220 ° C. Melt kneading in this temperature range is preferable because the polypropylene (A) is sufficiently melted and the crosslinking agent is completely decomposed. The time for melt kneading is generally 10 seconds to 5 minutes, preferably 30 seconds to 60 seconds. In the present invention, the kneaded product is then melt-kneaded with the polypropylene decomposable peroxide (C). This treatment results in a modified polypropylene that has suitable melting properties and can be taken up in a strand.

The melt-kneading of the kneaded product and the polypropylene decomposable peroxide (C) can be carried out by any of various methods. Preferably, the polypropylene (A) and the polypropylene-crosslinked peroxide (B) are mixed. After the melt-kneading, in a state where the kneaded material is still molten, it is preferable to add the polypropylene-decomposable peroxide (C) to the kneaded material and further melt-knead.

Specifically, using a twin screw extruder having at least two kneading units, a mixture of polypropylene (A) and polypropylene crosslinked peroxide (B) is supplied from a hopper and melt-kneaded. On the other hand, the polypropylene decomposable peroxide (C) is supplied from a side feed port provided in the middle of the extruder (between one kneading section and another kneading section), and the polypropylene (A) and the polypropylene crosslinked peroxide (B) are supplied. In addition to the melt-kneaded product of (1), a method of further melt-kneading may be used.

Polypropylene decomposable peroxide (C)
Can be usually performed by an auto feeder. Polypropylene decomposed peroxide (C)
May be a solid powder, a solution dissolved in a solvent, or an emulsion dispersed in water. The heating temperature at the time of melt-kneading the melt-kneaded product obtained by melt-kneading the polypropylene (A) and the polypropylene crosslinked peroxide (B) and the polypropylene-decomposed peroxide (C) is 160 to 250 ° C, preferably 170 to 220 ° C. It is. Melt kneading in this temperature range is preferred because the melt kneaded material is sufficiently melted and the composition obtained by completely decomposing the polypropylene-decomposable peroxide (C) does not change its properties further during molding. The time for melt kneading is generally 10 seconds to 5 minutes, preferably 30 seconds to 60 seconds.

[0033] The modified polypropylene thus obtained has a melt flow rate (ASTM D1238, 2).
30 ° C., load 2.16 kg) is preferably 0.1 to 15
g / 10 minutes, the melt tension is preferably in the range of 3 to 20 g, and the Mw / Mn determined by gel permeation chromatography is preferably 2 to 2.
The gel fraction by boiling para-xylene extraction is preferably in the range of 0.1 to 10% by weight.

Foam As a method for producing a foam from the modified polypropylene produced by the production method of the present invention, mainly the following two methods can be exemplified. (1) A method in which the modified polypropylene obtained by the above method, the decomposable foaming agent, and other additives as necessary are melted and heated to foam-mold. (2) A method in which a volatile foaming agent is pressed into molten polypropylene and then extruded by an extruder to obtain a foam.

The decomposition type foaming agent used in the above method (1) is a compound which decomposes the foaming agent to generate a gas such as carbon dioxide gas and nitrogen gas. And an organic acid which promotes gas generation may be added in combination. Specific examples of the decomposition type foaming agent include the following compounds. (A) Inorganic foaming agents: sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium carbonate, ammonium nitrite, citric acid, sodium citrate. (B) Organic foaming agents: N-nitroso compounds such as N, N'-dinitrosoterephthalamide, N, N'-dinitrosopentamethylenetetramine; azodicarbonamide, azobisisobutyronitrile, azocyclohexylnitrile, Azo compounds such as azodiaminobenzene and barium azodicarboxylate; benzenesulfonyl hydrazide;
Sulfonyl hydrazide compounds such as toluenesulfonyl hydrazide, p, p'-oxybis (benzenesulfenyl hydrazide), diphenylsulfone-3,3'-disulfonyl hydrazide; calcium azide, 4,4'-diphenyl disulfonyl azide, p-toluene Azide compounds such as sulfonyl azides.

Of these, carbonates or bicarbonates such as sodium bicarbonate are preferred. These decomposition type foaming agents can be used alone or in combination of two or more. The addition amount (kneading amount) of the decomposable foaming agent may be selected depending on the type of the foaming agent and the target expansion ratio, but is in the range of 0.5 to 100 parts by weight with respect to 100 parts by weight of the modified polypropylene. Preferably, there is.

If necessary, an organic carboxylic acid such as citric acid or a foam nucleating agent such as talc may be used in combination to control the cell diameter of the foam to an appropriate size. The foam nucleating agent used as needed is usually used by adding 0.01 to 1 part by weight to 100 parts by weight of the modified polypropylene.

In the method (1), the modified polypropylene and the decomposable blowing agent are both supplied to a melt extruder,
By generating a gas by thermally decomposing the foaming agent while melting and kneading at an appropriate temperature, by discharging the modified polypropylene in a molten state containing this gas from a die,
It can be formed into a foam. The melt-kneading temperature and the melt-kneading time in this method may be appropriately selected depending on the foaming agent and the kneading conditions to be used.

In the case of the above method (2), a volatile foaming agent can be used as the foaming agent. Preferred volatile foaming agents include, for example, aliphatic hydrocarbons such as propane, butane, pentane, hexane and heptane; cyclobutane,
Alicyclic hydrocarbons such as cyclopentane and cyclohexane; chlorodifluoromethane, difluoromethane, trifluoromethane, trichlorofluoromethane, dichloromethane, dichlorofluoromethane, dichlorodifluoromethane, trichlorofluoromethane, chloromethane, chloroethane, dichlorotrifluoroethane , Dichlorofluoroethane, chlorodifluoroethane, dichloropentafluoroethane, tetrafluoroethane, difluoroethane, pentafluoroethane, trifluoroethane,
Halogenated hydrocarbons such as dichlorotetrafluoroethane, trichlorotrifluoroethane, tetrachlorodifluoroethane, chloropentafluoroethane, and perfluorocyclobutane; inorganic gases such as carbon dioxide, nitrogen, and air; and water. These volatile foaming agents can be used alone or in combination of two or more.

The addition amount (kneading amount) of the volatile blowing agent in the above method (2) varies depending on the type of the blowing agent and the target expansion ratio, but is 0.5 to 100 parts by weight based on 100 parts by weight of the modified polypropylene. It is preferably within the range of parts. In the method (2), the modified polypropylene is melted in an extruder, the volatile foaming agent is pressed into the extruder, and kneaded with the modified polypropylene in a molten state while maintaining a high pressure. By extruding a kneaded product of the modified polypropylene and the volatile foaming agent kneaded in a die from a die, a foam can be formed. The melt-kneading temperature and the melt-kneading time in this method may be appropriately selected depending on the foaming agent to be used and the kneading conditions. The melt-kneading temperature is usually from 130 to 300 ° C., and the melt-kneading time is usually from 1 to 120 minutes. .

In both the method (1) and the method (2), melting is performed by an extruder, and a molten material having foam cells is discharged from a T-die or a cylindrical die, and preferably, a sheet is formed. Can be molded into a foam. In the case of discharging from a cylindrical die, usually, the cylindrical sheet is cut into one or a plurality of pieces, and then the smoothed sheet is taken out.

The foam according to the present invention is lightweight, heat insulating,
Terms cushioning or compressive strength of the external stress is suitable, preferably it has a density of 0.09~0.6g / cm ^3, especially 0.15 to 0.3 g / cm ³
Is more preferable. Therefore, the expansion ratio of the modified polypropylene is preferably in the range of 1.3 to 10 times, particularly 1.6 to 6 times.

Further, the foam of the present invention may have a closed cell ratio of 50% or more from the viewpoint that it has suitable heat resistance, good buffering of external force, and suitable compressive strength. It is more preferably 70% or more. In the method for producing a foam according to the present invention, the shapes that can be produced include a sheet shape, a board shape such as a board shape, a hollow shape such as a tube shape and a bag shape, a columnar shape, an elliptic columnar shape, a prismatic shape, and a strand shape. And various shapes such as columnar shape and particle shape.

Since the modified polypropylene obtained by the method of the present invention has a high melt tension and an appropriate MFR, it is particularly suitable for molding into a foamed sheet. The foamed sheet produced from this modified polypropylene has good secondary formation, and a large amount of trays and the like can be formed from the foamed sheet by hot-pressure forming or vacuum forming.

The polypropylene foam of the present invention is lightweight, has high rigidity, and is excellent in chemical resistance and food hygiene.
In particular, it can be used for cup ramen, ice cream containers, fish, meat trays, and the like.

[0046]

According to the present invention, a modified polypropylene having excellent fluidity, high melt tension and appropriate fluidity can be obtained. From this modified polypropylene, the foam according to the present invention, which is capable of forming a foam having excellent secondary processability, beautiful appearance, heat resistance, and excellent food hygiene, has excellent secondary processability, Beautiful appearance, excellent heat resistance and food hygiene.

[0047]

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples.

[0048]

Example 1 A screw arrangement was carried out so as to have two kneading parts, a first kneading part and a second kneading part.
Same-direction fully meshing twin-screw extruder with a screw rotation speed of 150 rpm (KZW25-, manufactured by Technobell Co., Ltd.)
30MG, screw diameter 31mmφ, L / D = 30)
Propylene homopolymer (trade name: J1
04, manufactured by Grand Polymer Co., Ltd., MFR: 8.0 g /
10 minutes) 100 parts by weight and 1.0 part by weight of bis (4-t-butylcyclohexyl) peroxydicarbonate (trade name: Percadox 16, manufactured by Kayaku Akzo Co., Ltd.) at 10 kg /
hr.

On the other hand, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane (trade name: Perhexin 25B,
Nippon Yushi Co., Ltd.) and propylene homopolymer (trade name: J1)
04, manufactured by Grand Polymer Co., Ltd.), a master powder diluted 1 / 50-fold was fed 100 g / h from a side feed port provided between the first kneading unit and the second kneading unit.
r by the automatic feeder at a speed of
The mixture was melt-kneaded at 0 ° C. for an average residence time of the resin of 30 seconds and melt-extruded to obtain pellets of the modified polypropylene A.

The pellets of the modified polypropylene A
MFR and melt tension were measured, and the gel fraction was calculated. Table 1 shows the results. For reference, the molecular weight distribution (Mw /
Mn). In addition, the melt flow rate (MFR) is 230 according to the method of ASTM D1238.
This is a value measured at a temperature of 2.degree.

The melt tension was measured by using a melt tension measuring device (manufactured by Toyo Seiki Seisaku-sho, Ltd.), an orifice (L = 8.00 mm, D = 2.095 mm), a set temperature: 230 ° C., and a piston descending speed of 30 mm / It is a value obtained by measuring the winding load of the pulley with load cell detection under the conditions of min and a winding speed of 4 mm / min. Mw, Mn
And Mz are values measured using GPC (gel permeation chromatography). For example,
Using a Waters 150C type machine, a Polymer Laboratories column PlmixedB was attached, and the measurement temperature was 13
5 ° C., o-dichlorobenzene was used as a solvent, 400 μl of a sample amount having a polymer concentration of 0.15% by weight was supplied, and M was obtained from a calibration curve prepared using standard polystyrene.
w, Mn and Mz can be determined.

The gel fraction was calculated by charging the sample of about 2 g into a # 400 mesh wire mesh, performing extraction for 6 hours by refluxing boiling para-xylene, and calculating from the weight of the material remaining in the wire mesh according to the following formula. Gel fraction (%) = (residual amount (g) / prepared amount (g))
× 100

[0053]

Example 2 The amount of bis (4-t-butylcyclohexyl) peroxydicarbonate used in Example 1 and the amount of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane supplied were respectively Modified polypropylene B was performed in the same manner as in Example 1 except that the weight was changed to 0.8 parts by weight and 50 g / hr.
I got Table 1 shows the property measurement results of the modified polypropylene B.

[0054]

Reference Example 1 Modified polypropylene C was obtained in the same manner as in Example 1, except that side feed of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane was not performed. . Table 1 shows the property measurement results of the modified polypropylene C.

[0055]

Example 3 100 parts by weight of modified polypropylene A pellets, a foaming agent masterbatch (trade name: PE-RM41)
OEN, 3 parts by weight of sodium bicarbonate / citric acid (manufactured by Dainichi Seika Co., Ltd.) were mixed for 3 minutes using a tumbler blender. The mixture was provided with a circular die of 80 mmφ and a mandrel of 190 mmφ at the tip.
Using a 5 mm single screw extruder (L / D = 28), a thickness of 0.1 mm was used.
An 8 mm annular foam sheet was formed. The expansion ratio of the annular foam sheet in this manufacturing apparatus was 2.4. One corner of the annular foamed sheet was cut open and taken out as a smooth sheet by a take-up machine.

The foamed sheet was evaluated for expansion ratio, appearance, cell shape and secondary formability (vacuum formability).
Table 2 shows the results. Sheet appearance: Visually evaluated according to the following evaluation criteria. ：: Unfoamed portion, unevenness and corrugate are not seen. X: Unfoamed portion, unevenness and corrugate are seen.

Expansion ratio (M): The apparent density (D) was calculated from the weight and the volume obtained by the submersion method, and the true specific gravity (0.
90) by "M = 0.90 / D". Cell shape: SEM observation of the cross section of the foam sheet was performed to observe the state of bubbles. The case where adjacent bubbles were independent of each other was evaluated as “independent”, and the case where they were connected was evaluated as “communication”, and evaluated.

Secondary workability: diameter 50 mm, depth 30
When the sheet was heated at 160 ° C. for 2 minutes and vacuum-formed using a mold capable of vacuum-forming three cups of 40 mm and 50 mm at the same time, the shape of the formed cup was good.
The appearance of the cup was evaluated in five stages (good: 5 ...
Poor: Evaluated in 1).

[0059]

Example 4 A foamed sheet having a thickness of 0.8 mm was formed in the same manner as in Example 3 except that the modified polypropylene composition B was used instead of the modified polypropylene composition A. This foam sheet was evaluated in the same manner as in Example 3. Table 2 shows the results.

[0060]

Reference Example 2 A foamed sheet having a thickness of 0.8 mm was formed in the same manner as in Example 3 except that the modified polypropylene composition C was used instead of the modified polypropylene composition A. This foam sheet was evaluated in the same manner as in Example 3. Table 2 shows the results.

[0061]

Comparative Example 1 In place of modified polypropylene composition A in Example 3, polypropylene propylene homopolymer (trade name: J104, manufactured by Grand Polymer Co., Ltd., MF
R: 8.0 g / 10 min), except that a foamed sheet having a thickness of 0.8 mm was formed in the same manner as in Example 3. This foam sheet was evaluated in the same manner as in Example 3. The vacuum forming was not able to form the drawdown severely. The results are shown in Tables 1 and 2.

[0062]

[Table 1]

[0063]

[Table 2]

Continued on the front page (72) Inventor Mikio Hashimoto 580-32, Takuji Nagaura, Sodegaura City, Chiba Prefecture Inside the Grand Polymer Co., Ltd. (72) Inventor Yoichi Wakida Takuji Nagaura, Sodegaura City, Chiba No. 32 F Term in Grand Polymer Co., Ltd. (Reference) 4F070 AA15 AC56 AE08 FA03 FB06 FC06 GA05 GA06 GC07 4F074 AA24 AD08 BA03 CA22 CC22X CC32X DA02 DA12 DA33 DA34 4J002 BB05W BB12W BB15W EK017 EK027 EK037 EK0EK EK037 EK037 EK037 EK037

Claims (7)

[Claims] 1. A polypropylene (A) and a polypropylene crosslinked peroxide (B) are melt-kneaded at 160 to 250 ° C., and the obtained kneaded product and a polypropylene decomposable peroxide (C) are melted at 160 to 250 ° C. A method for producing a modified polypropylene, comprising kneading. 2. The method for producing a modified polypropylene according to claim 1, wherein the polypropylene crosslinked peroxide (B) is a peroxydicarbonate. 3. The method according to claim 2, wherein the peroxydicarbonate is bis (4-t-butylcyclohexyl) peroxydicarbonate. 4. The method according to claim 2, wherein the peroxydicarbonate is dicetyl peroxydicarbonate. 5. The method for producing a modified polypropylene according to claim 1, wherein the polypropylene decomposable peroxide (C) is a dialkyl peroxide. 6. The method according to claim 5, wherein the dialkyl peroxide is 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane. 7. A foam obtained by foaming the modified polypropylene obtained by the method according to claim 1. Description: