JPH1135723A - Foam made of modified polypropylene-type resin composition and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a modified polypropylene foam with a good appearance which has a high expansion ratio and a high closed cell ratio as well as a large cross-sectional area of foaming, and to provide its manufacturing method. SOLUTION: A foam made of a modified polypropylene-type resin composition is obtained by melt mixing a polypropylene-type resin, a polyethylene-type resin, at least one monomer selected from the group consisting of isoprene monomer and 1,3-butadiene monomer, and a radical polymerization initiator. Its manufacturing is conducted by extrusion and foaming of a mixture of the composition and a foaming agent in the molten state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foam comprising a modified polypropylene resin composition and a method for producing the same. More specifically, the present invention comprises melt-kneading at least one monomer selected from a polypropylene resin, a polyethylene resin, an isoprene monomer and a 1,3-butadiene monomer, and a radical polymerization initiator. The present invention relates to a foam comprising a modified polypropylene resin composition to be obtained and a method for producing the same.

[0002]

2. Description of the Related Art In general, a foam made of a thermoplastic resin is lightweight and has good heat insulating properties and good buffering properties against external stress. Therefore, it is widely used as a heat insulating material, a cushioning material, a core material, a food container and the like. It's being used. Above all, foams made of a polypropylene-based resin have good chemical resistance, impact resistance, and heat resistance, and are therefore particularly preferably used as cushioning materials.

[0003] However, polypropylene resins are
Since it is a crystalline resin, the viscosity and tensile strength at the time of melting are low, and when the resin is foamed, the strength of the cell wall is not sufficiently maintained during foaming. Further, since this resin has a low gas barrier property, when the resin is foamed, the gas generated from the foaming agent is more easily scattered to the outside than the air bubbles. Therefore, it was difficult to obtain a low-density foam having an excellent appearance, a high closed cell ratio and a large cross-sectional area by foaming a polypropylene resin.

[0004] As a method of improving the foaming property of a polypropylene resin, a method of adding a crosslinking aid to a polypropylene resin to crosslink its molecules (Japanese Patent Publication No. 45-4042).
0) or a method of blending a polyethylene resin with a polypropylene resin and foaming the same (Japanese Patent Publication No. 44-25 / 1972)
74). However, even if these methods are used, the effect of improving foamability is not sufficient.

As described above, a method for improving the foaming property of a polypropylene resin and producing a low-density foam having an excellent appearance, a high closed cell ratio and a large cross-sectional area has not been found yet. It is the current situation.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a modified polypropylene foam having a high expansion ratio and closed cell ratio. It is still another object of the present invention to provide a modified polypropylene foam having a large cross-sectional area and a beautiful appearance, and a method for producing the same.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that a polypropylene resin, a polyethylene resin, an isoprene monomer and 1,
At least one monomer selected from 3-butadiene monomers, a radical polymerization initiator, at a temperature at which the polypropylene resin melts, and at a temperature at which the radical polymerization initiator can decompose, By subjecting the modified polypropylene resin composition obtained by kneading to extrusion foaming, it has been found that a low-density foam having a beautiful appearance, a high closed cell ratio and a large cross-sectional area can be obtained, and the present invention is completed. Reached.

According to the present invention, a polypropylene resin, a polyethylene resin, at least one monomer selected from an isoprene monomer and a 1,3-butadiene monomer, and a radical polymerization initiator are used. The present invention relates to a foam comprising a modified polypropylene resin composition obtained by melt-kneading at a temperature at which the radical polymerization initiator can be decomposed at a temperature at which the radical polymerization initiator can be decomposed.

Further, the present invention relates to a method for producing a foam comprising a modified polypropylene resin composition, comprising extruding a mixture comprising the modified polypropylene resin composition and a foaming agent in a molten state. It has never been known that if the modified polypropylene resin obtained by the present invention is subjected to extrusion foaming, it is possible to obtain a foam having a beautiful appearance, a high closed cell ratio, and a low density having a large cross-sectional area. That is surprising.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The raw material polypropylene resin usable in the present invention may be any of propylene homopolymer, block copolymer and random copolymer. Of these, propylene copolymers and propylene homopolymers containing 75% by weight or more of propylene are particularly preferred. The copolymerizable monomers in the polypropylene copolymer include, in addition to ethylene, butene-1, isobutene, pentene-1, 3-methyl-butene-1, hexene-1, 3-methyl-pentene-1, 4-
Methyl-pentene-1,3,4-dimethyl-butene-
Α-olefins having 4 to 12 carbon atoms, such as 1, 1, heptene-1, 3-methyl-hexene-1, octene-1, and decene-1; and cyclic olefins, such as cyclopentene and norbornene.

The polypropylene resin has a melt flow index (MI) of 2 according to JIS K7210.
At a load of 2.16 kg at 30 ° C., a workability of 0.2
Preferably, the viscosity is at least 20. From the viewpoint of maintaining the viscosity of the polypropylene resin composition at the time of melting to an extent suitable for foaming, the viscosity is preferably 20 or less, particularly preferably 10 or less.

Examples of the polyethylene resin include low-density polyethylene, high-density polyethylene, linear low-density polyethylene, and those obtained by modifying styrene, isoprene, and the like by graft copolymerization. Preferred is low density polyethylene. As described above, the polyethylene resin may be copolymerized with styrene, isoprene or the like, such as graft copolymerization, but the ethylene unit is preferably 80% by weight or more. The mixing ratio of the polyethylene resin to the polypropylene resin is preferably 1 to 40% by weight of the polyethylene resin to 60 to 99% by weight of the polypropylene resin.

The melt flow index (MI) of the polyethylene resin is preferably 0.1 or more from the viewpoint of processability, and the melt viscosity of the polypropylene resin composition is maintained at a level suitable for foaming. To 20 or less, preferably 10 or less. Examples of the radical polymerization initiator generally include a peroxide or an azo compound.In the present invention, the presence of a compound such as a radical polymerization initiator having a hydrogen abstraction ability with respect to the polymer molecule of the polypropylene resin is considered. is necessary.

Examples of the radical polymerization initiator include peroxides and azo compounds. Specific examples thereof include ketone peroxides such as methyl ethyl ketone peroxide and methyl acetoacetate peroxide;
1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) Peroxy ketals such as valerate, 2,2-bis (t-butylperoxy) butane; permethane hydroperoxide, 1,1,
3,3-tetramethylbutyl hydroperoxide,
Hydroperoxides such as 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-butyl peroxide, 2,5-dimethyl-2,5-di (t
Dialkyl peroxides such as -butylperoxy) hexine-3; diacyl peroxides such as benzoyl peroxide; di (3-methyl-3-methoxybutyl) peroxydicarbonate, di-2-methoxybutylperoxydicarbonate and the like T-butyl peroxy octate, t-butyl peroxy isobutyrate, t-butyl peroxy laurate, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxy octanoate Butylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate, t-butylperoxybenzoate, di-t-
One or more organic peroxides such as peroxyesters such as butyl peroxyisophthalate are exemplified. Among these, those having a high hydrogen abstracting ability are particularly preferable. As such a radical polymerization initiator,
For example, 1,1-bis (t-butylperoxy) -3,
3,5-trimethylcyclohexane, 1,1-bis (t
-Butylperoxy) cyclohexane, n-butyl-
4,4-bis (t-butylperoxy) valerate,
Peroxyketals such as 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-butylcumyl peroxide, di-t-butylperoxide, Dialkyl peroxides such as 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3; diacyl peroxides such as benzoyl peroxide; t-butylperoxyoctate, t-butylperoxyiso Butyrate, t-butylperoxylaurate, t-butylperoxy-3,5,5-trimethylhexanoate, t-
Butyl peroxyisopropyl carbonate, 2,5-
One or two of peroxyesters such as dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate, t-butylperoxybenzoate, and di-t-butylperoxyisophthalate;
More than seeds.

The amount of the radical polymerization initiator to be added is 0.05 to 100 parts by weight of the total amount of the polypropylene-based resin and the polyethylene-based resin in terms of optimizing the melt viscosity of the modified polypropylene-based resin and being economical. -5 parts by weight is preferred. The isoprene monomer and the 1,3-butadiene monomer may be used alone or in combination.
When used in combination, the usage ratio is arbitrary. The amount of the monomer (or monomer mixture) is preferably 0.1 to 50 parts by weight based on 100 parts by weight of the total of the polypropylene resin and the polyethylene resin. Further, 0.1 to 20 parts by weight is preferable from the viewpoint of compatibility between the resins.

The modified polypropylene resin composition includes:
If necessary, stabilizers or cross-linking agents such as antioxidants, metal deactivators, phosphorus-based processing stabilizers, ultraviolet absorbers, ultraviolet stabilizers, optical brighteners, metal soaps, antacid absorbers, and chain transfer Additives such as an agent, a nucleating agent, a lubricant, a plasticizer, a filler, a reinforcing agent, a pigment, a dye, a flame retardant, and an antistatic agent may be added as long as the object of the present invention is not hindered.

[0017] At least one monomer selected from such raw material polypropylene resin, polyethylene resin, isoprene monomer and 1,3-butadiene monomer,
The method of mixing and melt-kneading the radical polymerization initiator and other optional materials added as necessary are not particularly limited. For example, a raw material polypropylene-based resin, a polyethylene-based resin, an isoprene monomer and 1, At least one selected from 3-butadiene monomers
After mixing the seed monomers, the radical polymerization initiator and other optional materials added as necessary, the mixture may be melt-kneaded, or the mixture of the polypropylene-based resin and the polyethylene-based resin may be melt-kneaded. At least one monomer selected from an isoprene monomer and a 1,3-butadiene monomer, a radical polymerization initiator and other optional materials to be added as necessary, simultaneously or separately, They may be mixed together or divided and then melt-kneaded.

The melt kneading apparatus includes a roll,
Kneaders such as co-kneaders, Banbury mixers, Brabenders, single-screw extruders, twin-screw extruders, twin-screw surface renewers,
Examples of such a device include a horizontal stirrer such as a multi-shaft disk device or a vertical stirrer such as a double helical ribbon stirrer, which can heat a polymer material to an appropriate temperature and knead it while applying an appropriate shear stress. Of these, especially uniaxial or 2
A screw extruder is preferred in terms of productivity. In addition, the melt-kneading may be repeated a plurality of times in order to sufficiently and uniformly mix the respective materials.

As described above, the modified polypropylene resin composition of the present invention can be produced. As an example of the method for producing the foam of the present invention, after melt kneading the modified polypropylene resin composition and a foaming agent in a melt extruder, a method of obtaining a foam by extruding with a melt extruder, in a molten state After adding or press-fitting a foaming agent to the modified polypropylene resin composition, a method of obtaining a foam by extruding with a melt extruder can be used.

As the foaming agent, for example, propane,
Aliphatic hydrocarbons such as 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, difluoroethane, pentafluoroethane, trifluoroethane, dichlorotetrafluoroethane, trichloro Trifluoroethane, tetrachlorodifluoroethane, chloropentafluoroethane, perfluorocyclobutane What halogenated hydrocarbons; carbon dioxide, nitrogen, inorganic gases such as air; one or two or more of such water.

The addition amount (kneading amount) of the blowing agent varies depending on the type of the blowing agent and the target expansion ratio, but is 5 to 50 parts by weight based on 100 parts by weight of the modified polypropylene resin composition.
Preferably it is in the range of parts by weight. If necessary, a foam nucleating agent such as sodium bicarbonate-citric acid or talc may be used in combination in order to control the cell diameter of the foam to an appropriate size. Usually, the addition amount of the foaming nucleating agent used as needed is preferably 0.01 to 1 part by weight based on 100 parts by weight of the modified polypropylene resin composition.

In order to prevent shrinkage of the foam, a known shrinkage inhibitor may be used in combination, if necessary. Examples of the anti-shrinkage agent include fatty acids, partial esters of fatty acids and polyols, and fatty acid amides. The addition amount of the anti-shrinkage agent used as required is usually preferably 0.1 to 5 parts by weight based on 100 parts by weight of the modified polypropylene resin composition.

The foam of the present invention is a foam having an excellent tactile sensation, light weight, beautiful appearance, and a large cross-sectional area having a high closed cell ratio, and is useful for packaging materials, cushioning materials, heat insulating materials, and other uses. is there. Although the reason why the foamability of the modified polypropylene resin is remarkably improved in the present invention is not clear, according to the present invention, the compatibility between the polypropylene resin and the polyethylene resin which are not originally mixed is determined by the isoprene monomer and 1,1. This is considered to be due to the result of remarkably improved by at least one kind of monomer selected from 3-butadiene monomers and a radical polymerization initiator.

[0024]

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 closed cell ratio It was measured with an air pycnometer according to the method described in ASTM D-2856. 2) Measurement of foam density Measured according to JIS-K6767. 3) Cross-sectional magnification The cross-sectional magnification of the foam was calculated by dividing the cross-sectional area of the foam cured at room temperature for 24 hours after foaming by the cross-sectional area of the foamed die.

Cross sectional magnification (times) = (cross sectional area of foam) /
(Cross-sectional area of extrusion die) 4) Appearance The appearance of the foam was visually determined according to the following criteria. ○: Shrinkage and swelling of foam surface less than 10% △: Shrinkage of foam surface of 10% or more and less than 20% ×: Shrinkage and swelling of foam surface of 20% or more

[0026]

Example 1 95 parts by weight of ethylene random copolymerized polypropylene (3% by weight of ethylene, Hypol B230 manufactured by Grand Polymer Co., Ltd., MI = 0.5 g / 10 min), low-density polyethylene (manufactured by Sumitomo Chemical Co., Ltd.) Sumikacene F101-1, MI = 0.3) 5 parts by weight, α, α′-bis (t-butylperoxy-m-isopropyl) benzene (manufactured by NOF Corporation, perbutyl P, 1) as a radical polymerization initiator 0.25 parts by weight of a stabilizer (Irganox B22 manufactured by Ciba-Geigy)
5) A mixture comprising 0.2 parts by weight and 0.05 part by weight of a blended oil (Super Ease manufactured by Koshigaya Kasei Co., Ltd.) was stirred and mixed with a super floater. The mixture was put into a 44 mm twin-screw extruder (L / D = 38) hopper opening at 50 kg / hr using a measuring feeder, and an attached liquid feed pump was supplied so that isoprene became 1.25 kg / hr. (Diaphragm manufactured by Nikkiso Co., Ltd .: Model C22X-08
F-14D1D, discharge pressure 50 kgf / cm ² ), 2.5 parts by weight of isoprene was injected from the middle of the extruder cylinder. The mixture was extruded at a rotation speed of 150 rpm at 180 ° C. before injecting isoprene and at 200 ° C. after injecting to produce a modified polypropylene resin.

To 100 parts by weight of the modified polypropylene resin, 0.05 parts by weight of the blended oil and 0.1 parts by weight of sodium bicarbonate-citric acid as a cell nucleating agent were added and mixed with a superfloter. Then, the mixture was fed to a 40-50 mmφ tandem type extruder, and was fed into a first stage extruder (40 mmφ).
After melting at 00 ° C., 10 parts by weight of isobutane as a foaming agent was press-fitted and mixed with 100 parts by weight of the modified polypropylene resin, and the resin temperature was set to 1 by a second-stage extruder (50 mmφ).
After cooling to 40 ° C., the mixture was discharged from a cylindrical die (6 mmφ × 25 mm) under atmospheric pressure to obtain a round bar-shaped foam.

[0028]

Example 2 Example 1 was the same as Example 1 except that the low-density polyethylene was changed to linear low-density polyethylene (Mitsubishi Kasei Co., Ltd., Mitsubishi Polyethylene LL, UF420, MI = 0.8).

[0029]

Example 3 In Example 1, the radical initiator was 1,1-di (t-butylperoxy) -3,3,5-trimethylcyclohexane (manufactured by NOF Corporation, Perhexa 3M, 1
(Half-life at 147 ° C. for one minute) and the amount of the radical initiator was changed to 0.5 part.

[0030]

Example 4 Example 1 was the same as Example 1 except that isoprene was changed to 1,3-butadiene.

[0031]

Comparative Example 1 Same as Example 1 except that the ethylene random copolymerized polypropylene of Example 1 was used without modification.

[0032]

Comparative Example 2 Same as Example 1 except that the isoprene monomer and the radical initiator were not used.

[0033]

Comparative Example 3 Same as Example 1 except that low density polyethylene was not used.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

According to the present invention, at least one monomer selected from the group consisting of a polypropylene resin, a polyethylene resin, an isoprene monomer and a 1,3-butadiene monomer, and a radical polymerization initiator are melt-kneaded. By foaming the porous polypropylene resin composition, it is possible to produce a low-density foam having excellent tactile sensation, beautiful appearance, high closed cell ratio, and large cross-sectional area.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 23/10 C08L 23/10 B29K 9:00 23:00 105: 04

Claims (2)

[Claims] 1. Modification obtained by melt-kneading a radical polymerization initiator and at least one monomer selected from a polypropylene resin, a polyethylene resin, an isoprene monomer and a 1,3-butadiene monomer. A foam comprising a polypropylene-based resin composition. 2. A method for producing a foam comprising a modified polypropylene resin composition, comprising extruding a mixture comprising the modified polypropylene resin composition and a foaming agent in a molten state.