JPH0940725A - Modified polypropylene resin, its production, pre-expanded particle made of the same and expanded molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a modified polypropylene resin having a melting temperature peak lower than that of the unmodified polypropylene resin and therefore being capable of giving a final expanded molding at a lower temperature. SOLUTION: A modified polypropylene resin being a graft copolymer prepared by grafting an aromatic vinyl monomer onto a polypropylene resin, wherein the average number of aromatic vinyl graft chains is at least one per molecule of the graft copolymer, and the aromatic vinyl graft chain has a weight-average molecular weight of 200 or above, a process for producing the modified polypropylene resin, pre-expanded particles made of the modified polypropylene resin and a molding made of the pre-expanded particles are provided.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a modified polypropylene resin, a method for producing the modified polypropylene resin, pre-expanded particles of the modified polypropylene resin, and a foamed molded article of the pre-expanded particles.

[0002]

2. Description of the Related Art A foamed molded product of polypropylene resin is useful as a packaging material, a heat insulating material, a cushioning material or a core material and is widely used. Such polypropylene resin foam moldings can be manufactured by various manufacturing methods. One of them is to prepare pre-expanded particles once, put the pre-expanded particles in a desired mold and re-expand by steam or the like. The method (in-mold molding method) is used. Various methods have been carried out as a method for producing pre-expanded particles, for example, a method in which a polypropylene resin particle contains a foaming agent and is heated to foam (see, for example, JP-A-58-65734), polypropylene. There is known a method in which a foaming agent is contained in resin particles or pellets, heated and melted, and then extruded in a strand shape to foam (see, for example, JP-A-58-76230).

Conventionally, as a resin material for these pre-expanded particles of polypropylene resin, a homopolymer of propylene, a block copolymer of an α-olefin having 2 or 4 to 12 carbon atoms and propylene, or a carbon number of propylene is used. Random copolymers of 2 or 4 to 12 α-olefins with propylene have been used. Usually, the block copolymer and the random copolymer described above contain the α-olefin component having 2 or 4 to 12 carbon atoms in the range of about 25% by weight or less based on the whole.

However, particularly in the case of a propylene homopolymer and a block copolymer of an α-olefin having 2 or 4 to 12 carbon atoms and propylene, the peak value of the melting temperature of the resin itself (of the melting temperature measured by DSC) The peak value) is as high as about 160 ° C or higher, and the peak value of the melting temperature of the pre-expanded particles obtained from them is also about 160 ° C.
Above, and the portion annealed by the heat treatment in the pre-foaming step has a higher melting temperature peak value.

Further, the random copolymer has a lower peak value of melting temperature (about 130 to 160 ° C.) than the homopolymer of propylene and the block copolymer, but the polyethylene resin is still used. It is higher than the peak value of the melting temperature (about 100 to 130 ° C.). Further, the pre-expanded particles obtained from them also have the same or higher melting temperature peak value.

When the peak value of the melting temperature of the pre-expanded particles is high, the heating temperature at the time of re-foaming during the production of the foamed molded product is naturally high. In such a case, for example, in the in-mold molding method, the steam temperature must be raised, so the steam pressure must be increased, high energy is required, and the mold clamping force of the molding machine must be increased. There is a problem that it must be done.

As described above, there is a demand for pre-expanded particles capable of lowering the peak temperature of the melting temperature of the polypropylene resin and its pre-expanded particles and lowering the heating temperature during in-mold molding.

[0008]

The object of the present invention is to prevent the polypropylene resin from having mechanical properties such as rigidity and impact resistance, heat resistance or chemical resistance lower than the practically acceptable range. To obtain a modified polypropylene resin whose peak melting temperature is lower than the peak melting temperature of polypropylene resin before graft copolymerization by modifying the system resin and to melt using this modified polypropylene resin To obtain pre-expanded particles having a low temperature peak value. Another object of the present invention is to lower the molding temperature of the foamed molded product by using the pre-expanded particles.

[0009]

The present invention is a graft copolymer of a polypropylene resin and an aromatic vinyl monomer, wherein the grafted aromatic vinyl in one molecule of the graft copolymer. The average number of graft chains is 1 or more, and the weight average molecular weight of the aromatic vinyl graft chains is 20.
The present invention relates to a modified polypropylene resin having a value of 0 or more.

The average number of the aromatic vinyl graft chains is preferably 2 to 100, the weight average molecular weight of the aromatic vinyl graft chains is preferably 300 to 30,000, and the aromatic vinyl monomer is styrene,
It is preferably methylstyrene or divinylbenzene, and the molecular weight distribution of the modified polypropylene resin (Z average molecular weight (Mz) / weight average molecular weight (Mw))
Is preferably 3 or more.

According to the present invention, the modified polypropylene resin has a peak melting temperature lower than that of the polypropylene resin before graft copolymerization by 1 ° C. or more, preferably 5 ° C. or more. It relates to a polypropylene resin.

The modified polypropylene resin preferably has an equilibrium compliance of 10 × 10 ⁻⁴ m ² / N or more, and a recoverable shear strain per unit stress at a shear rate of 1 sec ⁻¹ is 3 × 10 ^−. It is preferably ⁴ m ² / N or more.

Even when the modified polypropylene resin is a graft copolymer composed of a polypropylene resin, an aromatic vinyl monomer, and another vinyl monomer copolymerizable with the aromatic vinyl monomer, Good.

The present invention is also a graft copolymer of a polypropylene resin and an aromatic vinyl monomer, wherein the average number of aromatic vinyl graft chains grafted onto one copolymer molecule is 1. The above is concerned with the pre-expanded particles comprising the modified polypropylene resin in which the weight average molecular weight of the aromatic vinyl graft chain is 200 or more.

With respect to the modified polypropylene resin constituting the pre-expanded particles, the average number of aromatic vinyl graft chains is preferably 2 to 100, and the weight average molecular weight of the aromatic vinyl graft chains is 300 to 30,000.
And the aromatic vinyl monomer is preferably styrene, methylstyrene or divinylbenzene. Further, the modified polypropylene resin preferably has a molecular weight distribution (Mz / Mw) of 3 or more.

Further, in the present invention, the peak value of the melting temperature of the modified polypropylene resin constituting the pre-expanded particles is 1 ° C. or higher than the peak value of the melting temperature of the polypropylene resin before graft copolymerization, preferably, It relates to pre-expanded particles lower by 5 ° C. or more.

The modified polypropylene resin constituting the pre-expanded particles has an equilibrium compliance of 10 × 10 ^-4 m
² / N or more is preferable, and the shear rate is 1
The recoverable shear strain per unit stress at sec ⁻¹ is preferably 3 × 10 ⁻⁴ m ² / N or more.

The present invention also relates to pre-expanded particles obtained by pre-expanding the modified polypropylene resin by using a melt extruder or cutting the pre-expanded polypropylene resin.

The present invention also relates to pre-expanded particles obtained by depressurizing and expanding the modified polypropylene resin.

The modified polypropylene resin constituting the pre-expanded particles is a graft copolymer comprising a polypropylene resin, an aromatic vinyl monomer and another vinyl monomer copolymerizable with the aromatic vinyl monomer. It may be a polymer.

In the present invention, a polypropylene resin is melt-kneaded with an aromatic vinyl monomer in the presence of a radical polymerization initiator to graft-copolymerize the polypropylene vinyl resin with the aromatic vinyl monomer. It consists of
TECHNICAL FIELD The present invention relates to a method for producing a modified polypropylene resin in which the number average number of aromatic vinyl graft chains grafted on one graft copolymer molecule is 1 or more and the weight average molecular weight of the aromatic vinyl graft chains is 200 or more. .

In the above production method, the average number of the aromatic vinyl graft chains is preferably 2 to 100, and the weight average molecular weight of the aromatic vinyl graft chains is preferably 300 to 30,000. The group vinyl monomer is preferably styrene, methylstyrene or divinylbenzene, and 0.1 to 100 parts by weight of the aromatic vinyl monomer, especially 1 to 50 parts by weight, relative to 100 parts by weight of the polypropylene resin. Melt kneading is preferable, and the radical polymerization initiator is peroxyketal, dialkyl peroxide,
It is preferably diacyl peroxide or peroxy ester.

In the present invention, 0.1 part of the radical polymerization initiator is added to 100 parts by weight of the polypropylene resin.
The present invention relates to a method for producing a modified polypropylene resin in which 10 to 10 parts by weight, preferably 0.5 to 5 parts by weight, is melt-kneaded.

In the above production method, it is preferable that the modified polypropylene resin has a molecular weight distribution (Mz / Mw) of 3 or more, and the peak value of the melting temperature of the modified polypropylene resin is before graft copolymerization. 1 ° C. or more lower than the peak value of the melting temperature of the polypropylene resin,
It is particularly preferable that the temperature is 5 ° C. or higher. Further, the equilibrium compliance of the modified polypropylene resin is 10 × 1.
It is preferably 0 ^-4 m ² / N or more, and the recoverable shear strain per unit stress when the modified polypropylene resin has a shear rate of 1 sec ^-1 is 3 × 10 ^-4 m ^2.
/ N or more is preferable.

In the above manufacturing method, a polypropylene resin is melt-kneaded with an aromatic vinyl monomer and another vinyl monomer copolymerizable with the aromatic vinyl monomer in the presence of a radical polymerization initiator. Thus, a method of graft-copolymerizing the aromatic vinyl monomer and another vinyl monomer copolymerizable with the aromatic vinyl monomer on the polypropylene resin may be used.

The present invention also relates to a foamed molded product obtained by in-mold molding of the pre-foamed particles.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION The modified polypropylene resin in the present invention is a graft copolymer obtained by subjecting a polypropylene resin before graft copolymerization to an aromatic vinyl monomer for a graft copolymerization reaction.

The peak value of the melting temperature of the modified polypropylene resin thus obtained is lower than the peak value of the melting temperature of the polypropylene resin before graft copolymerization.
Therefore, for example, when pre-expanded particles are produced by using the modified polypropylene resin, the pre-expanded particles can be pre-expanded at a lower temperature. Further, when the pre-expanded particles are molded in-mold to obtain a foam-molded article, this in-mold molding can be performed at a lower temperature.

Further, this modified polypropylene resin can be largely elastically deformed when melted. Therefore, this modified polypropylene resin has good extrusion foamability, and when melt-extruded and foamed using this modified polypropylene resin, it is easy to form pre-expanded particles having an appropriate expansion ratio.

The modified polypropylene resin is
By modifying the polypropylene-based resin before the graft copolymerization, the preferred properties of the polypropylene-based resin such as rigidity, chemical resistance, impact resistance and heat resistance are not lowered below the practical range.

Examples of the polypropylene resin before the graft copolymerization include homopolymers of propylene, block copolymers of propylene and other monomers, and random copolymers of propylene and other monomers. Examples of the crystalline polymer, the homopolymer is preferable from the viewpoint of high rigidity and low cost, and from the viewpoint that the peak value of the melting temperature is lower than other polymers, the propylene and other units A random copolymer with a polymer is preferred, and a block copolymer with the above-mentioned propylene and another monomer is preferred from the viewpoints of high rigidity and high impact resistance. When the polypropylene resin before graft copolymerization is a block copolymer or random copolymer of propylene and other monomers, high crystallinity, high rigidity and good chemical resistance characteristic of polypropylene resin From the point of retaining sex,
The content of the propylene monomer component contained is preferably 75% by weight or more, and more preferably 90% by weight or more.

In the polypropylene-based resin before the graft copolymerization, other monomers copolymerizable with propylene include a monomer composed of α-olefin, cyclic olefin, diene-based monomer and vinyl monomer. One or more monomers selected from the group Also,
This monomer is preferably an α-olefin or diene-based monomer because it is easily copolymerized with propylene and is inexpensive.

Examples of the above-mentioned α-olefin copolymerizable with propylene include ethylene, butene-1, isobutene, pentene-1,3-methyl-butene-1, hexene-1,3-methyl-pentene-1. , 4-methyl-pentene-1,3,4-dimethyl-butene-1, heptene-
Examples include α-olefins having 2 or 4 to 12 carbon atoms such as 1,3-methyl-hexene-1, octene-1 and decene-1. Further, examples of the cyclic olefin copolymerizable with propylene include cyclopentene, norbornene or 1,4,5,8-dimethano-1,2,2,
Examples include 3,4,4a, 8,8a-6-octahydronaphthalene. In addition, examples of the diene-based monomer copolymerizable with the propylene include 5-methylene-2-
Norbornene, 5-ethylidene-2-norbornene,
Examples thereof include 1,4-hexadiene, methyl-1,4-hexadiene, 7-methyl-1,6-octadiene and the like. Examples of the vinyl monomer copolymerizable with the propylene include vinyl chloride, vinylidene chloride, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, ethyl acrylate, butyl acrylate, methyl methacrylate , Maleic anhydride, styrene,
Examples include methylstyrene and divinylbenzene.

Of these monomers, ethylene or butene-1 is more preferable because it is inexpensive.

The molecular weight (weight average molecular weight) of the polypropylene resin before the graft copolymerization is preferably in the range of 50,000 to 2,000,000 from the viewpoint of easy industrial availability, and is inexpensive. More preferably, it is in the range of 100,000 to 1,000,000.

The molecular weight distribution (Mz / Mw) of the polypropylene resin before the graft copolymerization is preferably 2 or more from the viewpoint of industrial availability.
Molecular weight distribution of modified polypropylene resin (Mz / Mw)
Is more preferably 2.5 or more from the viewpoint of easily setting 3 or more. The reason why the modified polypropylene resin preferably has a molecular weight distribution (Mz / Mw) of 3 or more will be described later.

If necessary, other resins or rubbers may be added to the above polypropylene resin before graft copolymerization within a range not impairing the effects of the present invention. Examples of the other resin or rubber include polyethylene, polybutene-1, polyisobutene, polypentene-
1 or poly-α-olefins such as polymethylpentene-1, ethylene with a propylene content of less than 75% by weight
Propylene copolymer, ethylene / butene-1 copolymer or propylene containing less than 75% by weight of propylene /
Α-olefin / α-olefin copolymers such as butene-1 copolymers, α-olefin / α-such as ethylene / propylene / 5-ethylidene-2-norbornene copolymers having a propylene content of less than 75% by weight Olefin / diene monomer copolymer, 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, 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,
Α-olefin / vinyl monomer copolymer such as ethylene / methylstyrene copolymer or ethylene / divinylbenzene copolymer, polydiene copolymer such as polybutadiene or polyisoprene, styrene / butadiene random copolymer, etc. Vinyl monomer / diene monomer random copolymer, vinyl monomer / diene monomer / vinyl monomer block copolymer such as styrene / butadiene / styrene block copolymer, hydrogenation (styrene Hydrogenation (vinyl monomer / diene-based monomer random copolymer) such as / (butadiene random copolymer), hydrogenation (vinyl monomer / styrene / butadiene / styrene block copolymer) (vinyl monomer) / Diene monomer / vinyl monomer block copolymer), acrylonitrile / butadiene / styrene copolymer, Methacrylic acid methyl / butadiene / vinyl monomers such as styrene copolymer / diene monomer /
Vinyl monomers graft copolymers, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyvinyl acetate, ethyl polyacrylate, polybutyl acrylate, poly (methyl methacrylate) or vinyl polymers such as polystyrene or vinyl chloride / acrylonitrile. Examples thereof include vinyl copolymers such as copolymers, vinyl chloride / vinyl acetate copolymers, acrylonitrile / styrene copolymers, and methyl methacrylate / styrene copolymers.

The amount of the other resin or rubber added to the polypropylene resin before graft copolymerization varies depending on the type of the resin or the type of the rubber and is within the range not impairing the effects of the present invention as described above. Although it is good, it is usually preferably about 25% by weight or less.

Further, if necessary, the polypropylene resin before the graft copolymerization may include an antioxidant, a metal deactivator, a phosphorus processing stabilizer, an ultraviolet absorber, an ultraviolet stabilizer, an optical brightener, Stabilizers or crosslinkers such as metal soaps or antacid adsorbents, chain transfer agents, nucleating agents, lubricants, plasticizers,
Additives such as fillers, reinforcing materials, pigments, dyes, flame retardants or antistatic agents may be added within a range that does not impair the effects of the present invention.

The amounts of these stabilizers and additives are different from each other, but may be within the range not impairing the effects of the present invention as described above.

The polypropylene resin before graft copolymerization (which may include various additive materials) may be in the form of particles or pellets, and its size and shape are It is not particularly limited.

When the above-mentioned additive material (other resin, rubber, stabilizer or additive) is used, this additive material is previously added to the polypropylene resin before graft copolymerization. May be added when the polypropylene resin is melted, or may be added after the graft copolymerization.

Examples of the aromatic vinyl monomer include styrene; methylstyrene such as o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, β-methylstyrene, dimethylstyrene or trimethylstyrene. Α-chlorostyrene, β-
Chlorostyrene such as chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, dichlorostyrene or trichlorostyrene; o-bromostyrene, m-bromostyrene, p-bromostyrene, dibromostyrene or tribromostyrene, etc. Fluorostyrene such as o-fluorostyrene, m-fluorostyrene, p-fluorostyrene, difluorostyrene or trifluorostyrene; o-nitrostyrene, m-nitrostyrene, p-nitrostyrene, dinitrostyrene or trinitro Nitrostyrene such as styrene; vinylphenol such as o-hydroxystyrene, p-hydroxystyrene, m-hydroxystyrene, dihydroxystyrene or trihydroxystyrene; o-di Divinylbenzene such as nylbenzene, m-divinylbenzene or p-divinylbenzene; or one or two kinds of diisopropenylbenzene such as o-diisopropenylbenzene, m-diisopropenylbenzene or p-diisopropenylbenzene The above is mentioned. Of these, styrene, methylstyrene such as α-methylstyrene or p-methylstyrene, or divinylbenzene or a divinylbenzene isomer mixture is preferable because it is inexpensive.

The modified polypropylene resin of the present invention has one or more graft chains composed of the aromatic vinyl monomer grafted on average per modified polypropylene resin molecule.

The aromatic vinyl graft chain is preferably composed of one kind or two or more kinds of the aromatic vinyl monomer, but the aromatic vinyl monomer and the aromatic vinyl monomer are copolymerized. It may be formed by copolymerization with other possible vinyl monomers.

Other vinyl monomers copolymerizable with the aromatic vinyl monomer include, for example, vinyl chloride, vinylidene chloride, acrylonitrile, methacrylonitrile,
Acrylamide, methacrylamide, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, maleic anhydride,
Acrylic acid metal salt, methacrylic acid metal salt, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate or acrylate ester such as glycidyl acrylate, or methyl methacrylate, ethyl methacrylate , Butyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, glycidyl methacrylate, and other methacrylic acid esters.

In the case where the aromatic vinyl graft chain contains an aromatic vinyl monomer component and another vinyl monomer component copolymerizable with the aromatic vinyl monomer, the aromatic vinyl graft chain The other vinyl monomer component copolymerizable with the aromatic vinyl monomer is less than 100 parts by weight based on 100 parts by weight of the aromatic vinyl monomer component in the aromatic vinyl graft chain. It is preferably present, and more preferably less than 75 parts by weight on average. When the other vinyl monomer component that can be copolymerized with the aromatic vinyl monomer in the aromatic vinyl graft chain exceeds the above range, it is good when the strand is extruded and molded using this modified polypropylene resin. In some cases, it may not be possible to form suitable strands and obtain suitable pellets.

The modified polypropylene resin of the present invention should have, on average, one or more of the above aromatic vinyl graft chains grafted onto the molecular chain per one molecular chain. By this, the peak value of the melting temperature can be lowered, and when the pre-expanded particles are put in a desired mold and foamed again, in-mold molding can be performed at a low temperature. The average number of the graft chains is preferably in the range of 2 to 100, and more preferably in the range of 2 to 50. If the average number is less than the above range, the peak value of the melting temperature does not sufficiently decrease, while in order to exceed the above range, a large amount of radical polymerization initiator is generally required, and it is economically unsuitable. There is.

The number of aromatic vinyl graft chains is calculated by the following formula: (Number of aromatic vinyl graft chains) = (weight average molecular weight of modified polypropylene resin) × (1 part by weight of modified polypropylene resin) The number of parts by weight of the aromatic vinyl graft chain (there are cases where only the aromatic vinyl monomer is present and cases where the aromatic vinyl monomer and other vinyl monomer are included) / (Aromatic vinyl graft chain) The weight average molecular weight of

In addition, the vinyl monomer of the aromatic vinyl graft chain (which may be the case of only the aromatic vinyl monomer or the case of containing the aromatic vinyl monomer and another vinyl monomer) The weight average molecular weight is 200 or more from the viewpoint of increasing the number of graft chains and decreasing the peak value of the melting temperature, preferably in the range of 300 to 30,000, and more preferably in the range of 1,000 to 25,000. More preferable.

The peak value of the melting temperature can be lowered by grafting the aromatic vinyl graft chain on the polypropylene resin as described above.

In the modified polypropylene resin of the present invention, as an example of a preferable combination of the polypropylene resin before graft copolymerization and the aromatic vinyl monomer, the polypropylene resin before graft copolymerization is a polypropylene homopolymer, One or more of a propylene / ethylene random copolymer, a propylene / butene random copolymer, a propylene / ethylene block copolymer or a propylene / butene block copolymer, wherein the aromatic vinyl monomer is styrene, α-methylstyrene, p
-A combination of one or more of methylstyrene or divinylbenzene. Of these,
A combination in which the polypropylene resin before graft copolymerization is a polypropylene homopolymer, a propylene / ethylene random copolymer or a propylene / ethylene block copolymer, and the aromatic vinyl monomer is styrene is particularly preferable.

Further, it is preferable that the modified polypropylene resin has a molecular weight distribution (Z average molecular weight / weight average molecular weight) of 3 or more from the viewpoint that it can be largely elastically deformed when melted, and that the extrusion foamability is good. It is more preferably 3.5 or more from the viewpoint of being able to be largely elastically deformed when melted, or from the viewpoint of better extrusion foamability.

As described above, by grafting an aromatic vinyl graft chain onto the polypropylene resin before graft copolymerization, the modified polypropylene resin is modified with respect to the peak value of the melting temperature of the polypropylene resin before graft copolymerization. The peak value of the melting temperature of is decreased.

The peak value of the melting temperature of the modified polypropylene resin is preferably 1 ° C. or more, more preferably 5 ° C. or more lower than the peak value of the melting temperature of the polypropylene resin before graft copolymerization, and 5 to It is particularly preferable that the temperature is 30 ° C. lower. The difference between the peak value of the melting temperature of the modified polypropylene resin and the peak value of the melting temperature of the polypropylene resin before modification (the peak value of the melting temperature of the modified polypropylene resin is lower) is larger than 30 °. As described above, in order to modify the polypropylene-based resin particles before modification by graft copolymerization, a large amount of radical polymerization initiator is generally required, which may not be economically suitable.

Since the peak value of the melting temperature of the modified polypropylene resin is lower than the peak value of the melting temperature of the polypropylene resin before graft copolymerization by 1 ° C. or more, the foaming temperature at the time of depressurizing foaming and pre-expanded particles Since the molding temperature at the time of in-mold molding is low, for example, it is preferable in terms of energy, the fusion property of the pre-expanded particles is improved, and the appearance of the surface of the foamed molded product is improved. When the temperature is lower than the above, the foaming temperature during depressurization foaming and the molding temperature during in-mold molding of the pre-foamed particles are further lowered, which is further advantageous in terms of energy and the fusion property of the pre-foamed particles is further improved. Alternatively, it is preferable in that the appearance of the surface of the foamed molded product is further improved.

The peak of the melting temperature of the modified polypropylene resin is an aromatic vinyl monomer (or an aromatic vinyl monomer and another vinyl monomer copolymerizable with the aromatic vinyl monomer). ) Or radical polymerization initiator and the like, or the kneading conditions at the time of melt-kneading, if the graft polymerization occurs uniformly, it will have a single peak.

The modified polypropylene resin has a weight average molecular weight of 50,000 to 200 from the viewpoint that suitable strands are formed and suitable pellets (or particles) are obtained.
It is preferably 10,000, more preferably 100,000 to 1,000,000.

The modified polypropylene resin of the present invention has a peak melting temperature lower than the peak melting temperature of the polypropylene resin before graft copolymerization, and has practically used mechanical properties, heat resistance and chemical resistance. It is suitable as a material for pre-expanded particles in that it does not fall to the extent possible.

In addition, the modified polypropylene resin of the present invention can be cut satisfactorily because a strand obtained by foaming the modified polypropylene resin containing a foaming agent using an extruder or the like is easily cut by a rotary blade. It is also suitable as a material for obtaining pre-expanded particles by pre-expanding using an extruder or by cutting with a rotary blade or the like from the viewpoint that pre-expanded particles having a surface can be obtained.

The mechanism by which the workability (cuttability) of the polypropylene resin is improved by the above modification is not clear, but it is related to the fact that the polypropylene resin is likely to undergo melt elastic deformation by the graft copolymerization reaction. It is speculated that

Further, the modified polypropylene resin in the present invention has a low melting temperature peak value as described above, and is therefore particularly suitable as a pre-expanded particle material used for depressurized foaming. When the modified polypropylene resin of the present invention is used as a pre-expanded particle material used for depressurized foaming, the foaming temperature of the pre-expanded particles and the in-mold molding temperature can be lowered.

The pre-expanded particles in the present invention include bead-shaped or chopped strand-shaped pre-expanded particles.

Equilibrium compliance or recoverable shear strain per unit stress is a measure of the melt elastic deformation of the modified polypropylene resin. It can be said that the larger the equilibrium compliance or the recoverable shear strain per unit stress, the greater the melt elastic deformation. It is preferable that it is capable of being melt-elastically deformed to a greater extent, because pre-foaming with a good cut surface can be obtained when pre-foaming using, for example, an extruder.

From the above point, the equilibrium compliance of the modified polypropylene resin is 10 × 10 ⁻⁴ m ² / N.
It is preferably not less than 15 × 10 ⁻⁴ m ² / N and more preferably not less than 15 × 10 ⁻⁴ m ² / N. In addition, the recoverable shear strain per unit stress at a shear rate of 1 sec ⁻¹ of the modified polypropylene resin is 3 × 10 ⁻⁴ m from the above point.
It is preferably ² / N or more, more preferably 5 × 10 ⁻⁴ m ² / N.

The equilibrium compliance of the modified polypropylene resin was molded into a thickness of 1.4 mm and a diameter of 25 mm at a measurement temperature of 210 ° C. using a stress control type rheometer (DSR200 manufactured by Rheometrics Far East Co., Ltd.). A disc-shaped sample is sandwiched between parallel plates and 10,000N
The creep recovery value can be obtained by removing the stress after continuously applying a shear stress of / m ² for 300 seconds.

The recoverable shear strain per unit stress of the modified polypropylene resin was measured by using a strain control type rheometer (RDAII, manufactured by Rheometrics Far East Co., Ltd.).
At a measurement temperature of 210 ° C., thickness 1.4 mm, sandwiched between a cone and a flat plate sample in the shape of a disk with a diameter of 25 mm, followed twisting at a constant strain rate, shear rate along with the first normal stress and shear stress 1 sec ^- Measure the value at ^{1 and use} the following formula:
(Recoverable shear strain per unit stress) = (first normal stress) / 2 (shear stress) ² can be calculated.

When the above-mentioned equilibrium compliance and recoverable shear strain are less than the above ranges, for example, a strand obtained by foaming a modified polypropylene resin with a foaming agent using an extruder or the like becomes difficult to cut.
There is a case where a cut surface is worn.

The modified polypropylene resin can be obtained by melt-kneading the polypropylene resin before graft copolymerization with an aromatic vinyl monomer in the presence of a radical polymerization initiator. Further, the other resin (a resin other than the polypropylene resin before the graft copolymerization) or rubber may be melt-kneaded together.

The aromatic vinyl graft chain may be formed by copolymerization of the aromatic vinyl monomer and another vinyl monomer copolymerizable with the aromatic vinyl monomer. In this case, the graft copolymerization reaction initiates radical polymerization of an aromatic vinyl monomer, another vinyl monomer copolymerizable with the aromatic vinyl monomer, and the polypropylene resin before the graft copolymerization. It can be carried out by a method such as melt kneading in the presence of an agent.

If necessary, the above-mentioned stabilizers and additives may be melt-kneaded together.

The amount of the aromatic vinyl monomer to be melt-kneaded is the polypropylene resin 1 before graft copolymerization.
The amount is preferably 0.1 to 100 parts by weight, more preferably 1 to 50 parts by weight, based on 00 parts by weight. When the amount of the vinyl monomer is less than the above range, the average number of aromatic vinyl graft chains is less than 1 per molecule of the modified polypropylene resin which is the obtained graft copolymer. In this case, the peak value of the melting temperature tends not to be lowered sufficiently. On the other hand, when the amount of the vinyl monomer exceeds the above range,
Since a large amount of radical polymerization initiator is required, the cost tends to be disadvantageous.

As the radical polymerization initiator, a peroxide or an azo compound is generally used. In order for the graft copolymerization reaction to occur between the polypropylene-based resin and the vinyl monomer, the presence of a compound having a so-called hydrogen abstraction ability is necessary. Generally, a ketone peroxide such as methyl ethyl ketone peroxide or methyl acetoacetate peroxide is used. Oxide; 1,1-bis (t
-Butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) valerate or 2,2 -Peroxyketals such as bis (t-butylperoxy) butane; hydroperoxides such as permentan hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, diisopropylbenzene hydroperoxide or cumene hydroperoxide Peroxide; dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, α, α'-bis (t-butylperoxy-m-isopropyl) benzene, t-butyl Cumyl peroxide, di-t-butyl peroxide or 2, -Dialkyl peroxide such as dimethyl-2,5-di (t-butylperoxy) hexyne-3; diacyl peroxide such as benzoyl peroxide; di (3-methyl-3-methoxybutyl) peroxydicarbonate or di Peroxydicarbonate such as 2-methoxybutylperoxydicarbonate; or t-butylperoxyoctate, t-butylperoxyisobutyrate, t-butylperoxylaurate, t-butylperoxy-3,
5,5-trimethylhexanoate, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-
Organic peroxides such as peroxyesters such as 2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate, t-butylperoxybenzoate or di-t-butylperoxyisophthalate may be mentioned. Of these, those having a particularly high hydrogen abstraction ability are preferable, and examples thereof include 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane,
Peroxyketals such as 1,1-bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) valerate or 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-butylcumylper Dialkyl peroxide such as oxide, di-t-butyl peroxide or 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, diacyl peroxide such as benzoyl peroxide or t-butylperoxide Oxyoctate, t-
Butyl peroxyisobutyrate, t-butyl peroxylaurate, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxyisopropyl carbonate, 2,5-dimethyl-2,5- One or more of peroxyesters such as di (benzoylperoxy) hexane, t-butylperoxyacetate, t-butylperoxybenzoate or di-t-butylperoxyisophthalate may be used.

From the viewpoint that the peak value of the melting temperature of the modified polypropylene resin is lower than the peak value of the melting temperature of the polypropylene resin before graft copolymerization, and it is economical, the radical polymerization initiator is used. When the material to be melt-kneaded does not contain the other resin or rubber, 100 parts by weight of the polypropylene resin before graft copolymerization is added to the propylene resin. It is preferably in the range of 0.1 to 10 parts by weight, and more preferably in the range of 0.5 to 5 parts by weight, based on 100 parts by weight of the total of the resin and other resin and / or rubber. preferable.

When the modified polypropylene resin of the present invention is produced by using a large amount of radical polymerization initiator as compared with the conventional one, the aromatic polypropylene grafted on one modified polypropylene resin molecule. The average number of vinyl graft chains can be particularly higher than the number of graft chains of the conventionally known modified polypropylene resin.

The addition amount of the other vinyl monomer which may be melt-kneaded with the above aromatic vinyl monomer is less than 100 parts by weight based on 100 parts by weight of the aromatic vinyl monomer. Is preferable, and less than 75 parts by weight is more preferable. If the addition amount of the other vinyl monomer exceeds the above range, suitable strands cannot be formed, and therefore suitable pellets cannot be obtained.

The amount of the resin or rubber that may be melt-kneaded together may be within the range that does not impair the effects of the present invention as described above, but is preferably 25% by weight or less of the total amount. .

Further, the above-mentioned stabilizers and additives are added in appropriate amounts as needed.

As an example of a suitable combination of the polypropylene resin before the graft copolymerization, the aromatic vinyl monomer and the radical polymerization initiator, the polypropylene resin before the graft copolymerization is a polypropylene homopolymer or propylene. / Ethylene random copolymers, propylene / butene random copolymers, propylene / ethylene block copolymers or propylene / butene block copolymers, and the aromatic vinyl monomer is styrene.
One or more of α-methylstyrene, p-methylstyrene or divinylbenzene, and the radical polymerization initiator is α, α′-bis (t-butylperoxy-m-
Isopropyl) benzene, 2,5-dimethyl-2,5-
Di (t-butylperoxy) hexyne-3, or di-
Examples thereof include a combination of one or more t-butyl peroxides. When a rubber or another resin is added to these, ethylene is used as a rubber component or another resin component in the above combination. / Propylene copolymer, ethylene / propylene / diene copolymer, polybutadiene, polyisoprene, styrene / butadiene random copolymer, styrene / butadiene / styrene block copolymer, polyethylene, ethylene / vinyl acetate, ethylene / (meth) A combination in which one or more metal acrylates or polystyrenes are added may be used. The modified polypropylene resin composed of the combination as described above is particularly suitable for decreasing the peak value of the melting temperature, and the foaming temperature and in-mold molding temperature of the pre-expanded particles are suitably decreased, and at the time of melting. It has a characteristic that it can be greatly elastically deformed and has excellent foaming properties even when it is subjected to extrusion foaming or depressurization foaming.

As a particularly preferable combination of the polypropylene resin before the graft copolymerization and the aromatic vinyl monomer, the polypropylene resin before the graft copolymerization is a polypropylene homopolymer or a propylene / ethylene random copolymer. Examples thereof include polymers or propylene / ethylene block copolymers in which the aromatic vinyl monomer is styrene, and in this case, the radical polymerization initiator is exemplified in the above-mentioned suitable combination examples. Any of them is preferably used.

The order and method of mixing and melt-kneading these modified polypropylene resin, aromatic vinyl monomer, radical polymerization initiator and other added materials are not particularly limited. The polyolefin resin before copolymerization, the aromatic vinyl monomer, the radical polymerization initiator and other additive materials added as necessary may be mixed and then melt kneaded, or the polyolefin resin is melt kneaded. After that, the aromatic vinyl monomer, the radical polymerization initiator, and other additional materials to be added if necessary may be mixed simultaneously or separately, collectively or in a divided manner. The heating temperature at the time of melt-kneading is 130 to 400 ° C. The polypropylene resin before modification is sufficiently melted and is not thermally decomposed,
It is preferable in that the above radical reaction sufficiently occurs. The melt-kneading time (time after mixing the radical polymerization initiator and the aromatic vinyl monomer) is generally 1 to
60 minutes.

As the melt-kneading device, a kneader such as a roll, a co-kneader, a Banbury mixer, a Brabender, a single-screw extruder or a twin-screw extruder, a twin-screw surface renewing machine, or a twin-screw multi-disc device is used. Examples include a horizontal stirrer such as or a vertical stirrer such as a double helical ribbon stirrer, which can heat a polymer material to an appropriate temperature and knead while applying an appropriate shear stress. Of these,
An extruder is particularly preferable in terms of productivity. The melt-kneading may be repeated a plurality of times in order to mix the respective materials sufficiently uniformly.

The modified polypropylene resin of the present invention can be produced as described above.

When the modified polypropylene resin is subjected to depressurization foaming to give pre-expanded particles, the modified polypropylene resin is usually molded into particles or pellets. A method of molding the modified polypropylene resin into particles or pellets can be performed by a conventionally known method.

In the case of depressurized foaming, the preferred form of the modified polypropylene resin particles or pellets is as follows.
From the viewpoint of easy filling of the pre-expanded particles composed of the particles or pellets into the in-mold molding die, it is preferable that the particles have a spherical shape or a shape close to a spherical shape. When the modified polypropylene resin has a spherical shape, the diameter of the pre-expanded particles obtained by pre-expanding particles or pellets of the modified polypropylene resin is 0.
It is preferable to adjust the diameter of the particles or pellets of the modified polypropylene resin so as to be about 3 to 10 mm. If the shape of the particles or pellets is not spherical, it is preferable to adjust the diameter of the particles or pellets of the modified polypropylene resin so that the particles or pellets have the same size as the spherical shape.

The pre-expanded particles can be usually produced by first adding a foaming agent to the particles or pellets of the modified polypropylene resin, and then pre-expanding them.

The method of pre-foaming the modified polypropylene resin particles or pellets with a foaming agent is not particularly limited. For example, the particles or pellets may be impregnated with a gaseous foaming agent. Pre-expanding method (method of impregnating in gas phase for pre-foaming), method of impregnating particles or pellets with a foaming agent in a liquid state and pre-foaming (method of impregnating in liquid phase and pre-foaming), particles or A method of pre-expanding by impregnating a foaming agent in a state where pellets are dispersed in water (a method of impregnating and pre-foaming in a water dispersion system) or kneading a foaming agent in a state where these particles or pellets are melted in an extruder. And a method of pre-foaming (a method of impregnating with an extruder for pre-foaming). Of these, the method of impregnating with the water dispersion system and pre-foaming or the method of impregnating with an extruder and pre-foaming is particularly preferable from the viewpoint of productivity.

Preferred blowing agents are, for example, aliphatic hydrocarbons such as propane, butane, isobutane, pentane, hexane or heptane, cycloaliphatic hydrocarbons such as cyclobutane, cyclopentane or cyclohexane, chlorodifluoromethane, dichloromethane, Halogenated hydrocarbons such as dichlorofluoromethane, dichlorodifluoromethane, trichlorofluoromethane, chloroethane, dichlorotrifluoroethane, dichlorotetrafluoroethane, trichlorotrifluoroethane, tetrachlorodifluoroethane or perfluorocyclobutane or carbon dioxide, nitrogen or One or more inorganic gases such as air may be used.

The addition amount (kneading amount) of the foaming agent depends on the type of the foaming agent and the target expansion ratio, but the modified polypropylene resin (rubber and / or other resin other than the polypropylene resin is mixed with the polypropylene resin). In this case, the modified polypropylene resin may be a modified polypropylene resin. In this case, the modified product of this mixture is referred to as a modified polypropylene resin.
It is usually in the range of 00 parts by weight, and preferably in the range of 1 to 50 parts by weight from the viewpoint of cost.

In order to control the bubble diameter of the foamed body to an appropriate size, sodium bicarbonate may be added, if necessary.
A foam nucleating agent such as citric acid or talc may be used in combination. The nucleating agent for foaming, which is used as necessary, is usually used by adding 0.1 to 1 part by weight to 100 parts by weight of the modified polypropylene resin.

The pre-foaming method is not particularly limited and may be a conventionally known method.

When the modified polypropylene resin is pre-expanded with a melt extruder or cut and then pre-expanded particles are obtained, the modified polypropylene resin is obtained by using, for example, a melt extruder. After melting in the first stage extruder, press the foaming agent under pressure, melt and knead by a method in which the foaming agent is melt-mixed with the resin in the molten state while cooling in the second stage extruder, and in a room temperature atmosphere from a circular die. It can be performed by a conventionally known method such as extruding into a foamed strand and cutting the foamed strand with a rotary blade to form a pre-foamed body.

Examples of the melt extruder include conventionally known ones such as a tandem type extruder in which a foaming agent can be pressed.

The foaming agent is not particularly limited, and examples thereof include normal butane, isobutane, and a mixed gas thereof. The amount of the foaming agent added is usually in the range of 1 to 100 parts by weight with respect to 100 parts by weight of the modified polypropylene resin component, and in the range of 1 to 50 parts by weight, the cost is low. It is preferable from the aspect.

The set temperature of the melt extruder varies depending on the type of the modified polypropylene resin or the type or amount of the foaming agent. For example, the peak value of the melting temperature of the modified polypropylene resin is 140 to 160 ° C. In this case, the first-stage extruder has a temperature of about 230 ° C. to sufficiently melt the modified polypropylene resin, and the second-stage extruder has the modified polypropylene resin at a melting temperature near the peak value or at a melting temperature. 140 ~ for cooling below the peak value
An example of a preferable temperature is about 150 ° C.

When a modified polypropylene resin in a molten state containing the foaming agent is discharged, a porous circular die having a die hole diameter of about 0.2 to 3 mm can be preferably used as an example of a die. can give.

The diameter of the foamed strand is 0.3 to 1
It is preferably about 0 mm. The pre-expanded particles can be obtained by, for example, cutting the expanded strand with a rotary blade.

The cutting width of the foamed strand is 0.3 to 1
It is preferably about 0 mm, preferably about 0.5 to 8 mm, from the viewpoint of easy filling of the obtained pre-expanded particles into the in-mold molding die.

In the production of each of the pre-expanded particles, the expansion ratio of the pre-expanded particles is usually in the range of 2 to 100 times, but the external force which is one of the characteristics of the foam-molded article. 10-8 from the viewpoint of making the buffering performance of
More preferably, it is within the range of 0 times.

Since the pre-expanded particles of the present invention are manufactured by using the modified polypropylene resin of the present invention as described above, the fusion of the pre-expanded particles is lower than that of the conventional polypropylene resin. It can happen at temperature. Therefore, when the pre-expanded particles of the present invention are used, a foamed molded article can be obtained at a low foaming molding temperature.

The method for molding the foamed molded article is not particularly limited, but, for example, a method of filling pre-expanded particles in a mold and then introducing steam into the mold to re-expand the pre-expanded particles. , A method of filling the pre-expanded particles in a mold and then compressing under heating, a method of filling the pre-expanded particles in a mold in a heated and pressurized state or pre-expanded particles 2
Known methods include, for example, a method in which after-foaming ability is imparted and then the mixture is filled in a mold under heating.

The characteristics of the resin component of the pre-expanded particles and the foamed molded product thus produced are almost the same as the characteristics of the modified polypropylene resin used for the production thereof. That is, the resin component of the pre-expanded particles and the foamed molded article is a graft copolymer of a polypropylene resin (which may contain rubber and / or resin) and an aromatic vinyl monomer. This is a modified polypropylene resin in which the average number of grafted aromatic vinyl graft chains in one copolymer molecule is 1 or more, and the weight average molecular weight of the aromatic vinyl graft chains is 200 or more. The average number of aromatic vinyl graft chains of this resin component is preferably 2 to 100, and the weight average molecular weight of the aromatic vinyl graft chains is 300 to 300.
00, the aromatic vinyl monomer is preferably styrene, methylstyrene or divinylbenzene, and the modified polypropylene resin has a molecular weight distribution (Z average molecular weight (Mz) / weight average molecular weight ( It is preferred that Mw)) is 3 or more. The peak value of the melting temperature of this resin component is 1 ° C. or more, preferably 5 ° C. or more, particularly preferably 5 to 3 lower than the peak value of the melting temperature of the polypropylene resin before graft copolymerization.
It is a modified polypropylene resin that is lower than 0 ° C. Also,
The equilibrium compliance of this resin component is 10 × 10 ^-4 m
² / N or more is preferable, and the shear rate is 1 s
The recoverable shear strain per unit stress at ec ^-1 is 3
It is preferably × 10 ⁻⁴ m ² / N or more. Further, the resin component may be a graft copolymer composed of a polypropylene resin, an aromatic vinyl monomer and another vinyl monomer copolymerizable with the aromatic vinyl monomer.

The expansion ratio of the foamed molded product is usually in the range of 2 to 100 times.
It is more preferable to be in the range of 10 to 80 times from the viewpoint of making the shock absorbing performance of external force, which is one of the characteristics of the foamed molded article, suitable.

Next, the present invention will be explained based on examples, but the present invention is not limited to these.

[0105]

【Example】

Example 1 100 parts by weight of a propylene homopolymer (Sumitomo Chemical Co., Ltd., Nobrene D501), 20 parts by weight of styrene (Wako Pure Chemical Industries, Ltd., special grade), and α, α'-as a radical polymerization initiator. Bis (t-butylperoxy-m-isopropyl) benzene (produced by NOF CORPORATION, perbutyl P,
1 minute half-life temperature 175 ° C) 3.5 parts by weight,
It was supplied to a twin-screw extruder (LABOTEX) manufactured by Japan Steel Works in a state where the propylene homopolymer was impregnated with styrene in advance and the radical polymerization initiator was blended.

The peak value of the melting temperature of the propylene homopolymer before being fed to the twin-screw extruder is measured by a differential scanning calorimetry (DSC) device (manufactured by Perkin Elmer Japan Co., Ltd.,
Using DSC-7), the sample weight was set to 10 mg, the temperature was raised to 200 ° C. at 50 ° C./min in a nitrogen atmosphere, this temperature was kept for 5 minutes, and the temperature was lowered to 50 ° C. at 10 ° C./min. The temperature was maintained for 5 minutes, and then the temperature was raised at 10 ° C./minute to measure 160 ° C. The peak value of the melting temperature was the main peak of the endothermic peaks detected when measured under the above conditions.

The twin-screw extruder was of the same-direction, twin-screw type, the hole diameter of the cylinder was 32 mmφ, and the maximum effective screw length (L / D) was 25.5. The twin-screw extruder was heated at a set temperature of the cylinder section of 200 ° C. and at a set temperature of the feed section of 160 ° C., and the rotation speed of the screw was set to 100 rpm for each axis.

By performing melt extrusion in this state, a rod-shaped modified polypropylene resin molded product having a diameter of 4 mm was obtained. This rod-shaped molded product of the modified polypropylene resin was shredded to a thickness of 3 mm to obtain resin pellets.

The peak value of the melting temperature of the modified polypropylene resin was measured by the same method as the peak value of the melting temperature of the polypropylene resin before graft copolymerization, and was 147 ° C.

The DSC pattern of the modified polypropylene resin measured by the differential scanning calorimeter is shown in FIG.
Shown in In FIG. 1, the horizontal axis represents temperature and the vertical axis represents the amount of heat.

Next, the number of aromatic vinyl graft chains of this modified polypropylene resin was calculated by the following formula: (Number of aromatic vinyl graft chains) = (weight average molecular weight of modified polypropylene resin) × (modified polypropylene) It was determined by the following formula: (part by weight of aromatic vinyl graft chain grafted onto 1 part by weight of resin) / (weight average molecular weight of aromatic vinyl graft chain).

The weight average molecular weight of the modified polypropylene resin is determined by high temperature gel permeation chromatography (GP) of the xylene insoluble matter of the modified polypropylene resin.
C) (refractive index (RI) detector) (manufactured by Japan Waters Limited, 150CV GPC system) was measured, and it was determined by polystyrene conversion. Further, the number of parts by weight of the aromatic vinyl graft chain grafted onto 1 part by weight of the modified polypropylene resin is the infrared spectrophotometer (IR) of the modified polypropylene resin (Shimadzu Corporation). Manufactured by FTIR8100 system), and the height of the peak near 1370 cm ⁻¹ derived from polypropylene and the height of the peak derived from the aromatic vinyl monomer (here, the height of the peak near 700 cm ⁻¹ derived from the benzene ring). ) And the ratio. The weight average molecular weight of the aromatic vinyl graft chain is determined by measuring the xylene-soluble component of the modified polypropylene resin at room temperature GPC (UV spectrophotometer (UV) detector) (510 GPC manufactured by Japan Waters Limited).
System) and converted into polystyrene. As a result, the weight average molecular weight of the modified polypropylene resin was 628,000, and the number of parts by weight of the aromatic graft chain grafted on 1 part by weight of the modified polypropylene resin was 0.062. The weight average molecular weight was 8800 and the number of aromatic vinyl graft chains was 4.4.

Next, pre-expanded particles were produced using the modified polypropylene resin.

100 parts by weight of the modified polypropylene resin pellets, 12 parts by weight of butane gas, 2 parts by weight of tricalcium phosphate, 0.05 parts by weight of sodium dodecylbenzenesulfonate, and 300 parts by weight of water were placed in a closed container, The mixture was thoroughly stirred to sufficiently disperse the solid component and the gas component in water. While stirring, keep the closed container 6
The temperature was raised to 148 ° C over 0 minutes, and the pressure in the closed container was adjusted to 20 kgf / cm ² while continuing stirring, and 1
Hold for 5 minutes. The pressure in the closed container is 20 kgf / cm ²
Pre-expanded particles were obtained by releasing one end of the closed container while maintaining the temperature at 1, and discharging the resin pellet together with other components into the atmosphere at room temperature (hereinafter, also referred to as pre-expanded particle production condition 1).

The expansion ratio of the pre-expanded particles was obtained by the following formula: (volume of foam / weight of foam) × 0.9 (where 0.9 is the approximate density of the modified polypropylene resin). Is). As a result, the expansion ratio of the pre-expanded particles was 17 times.

The pre-expanded particles were transferred to another closed container,
At 80 ° C, the air inside this closed container is 7 kgf / cm.
Pressurized to ^{2 and} held for 1 hour.

Then, about 13 pre-expanded particles after pressure treatment
6 g was filled in a molding die having a cavity of 25 cm × 25 cm × 5 cm and molded at 12 levels at 130 ° C. to 163 ° C. at 3 ° C. intervals to obtain foamed molded products under the respective conditions. The fusion rate of pre-expanded particles of these foamed molded articles, the foamed molded article is fractured by human power, and the ratio of the number of fused particles to the total number of particles in this fracture surface is measured visually, The relationship between the molding temperature condition and the fusion rate was determined, and the in-mold molding temperature at which the fusion rate (the ratio of the number of fused particles to the total number of particles shown in the cross section) exceeded 60% was determined. To determine whether the particles are fused or not fused, it is visually evaluated whether breakage occurs inside the particle or at the particle interface, and this breakage occurs inside the particle due to fusion. I decided to do it. As a result, the in-mold molding temperature at which the fusion rate exceeded 60% was 151 ° C or higher.

In addition, in the evaluation of the fusion rate, the in-mold molding temperature at which the fusion rate exceeds 60% (in this case, 15
The expansion ratio of the foamed molded product at 1 ° C.) was measured by the same method as the method for measuring the expansion ratio of the pre-expanded particles. As a result, the expansion ratio of this foamed molded product was 20 times.

Next, pre-expanded particles were prepared under different molding conditions.

The modified polypropylene resin pellet 1
100 parts by weight, 0.1 part by weight of sodium bicarbonate-citric acid (manufactured by Eiwa Kasei Co., Ltd., Cerbon SG / IC) and 0.05 part by weight of process oil (Super Ease, manufactured by Koshigaya Kasei Kogyo Co., Ltd.) After mixing, the mixture was supplied to a tandem type extruder and melted in a first stage extruder (cylinder inner diameter: 40 mmφ) in which the cylinder temperature was set to 230 ° C. Then, butane gas was added to 100 parts by weight of the modified polypropylene resin pellets. While press-fitting at a rate of 5 parts by weight, these were mixed in a second stage extruder (cylinder inner diameter: 50 mmφ) in which the cylinder temperature was set to 150 ° C., and then a foamed resin strand with a diameter of 4 mm was passed from a circular die to room temperature. Was extruded into the atmosphere and cut with a rotary blade to a thickness of 3 mm to obtain pre-expanded particles (hereinafter also referred to as pre-expanded particle production condition 2). .

The expansion ratio of the pre-expanded particles was measured by the same method as the measurement of the expansion ratio of the pre-expanded particles manufactured under the pre-expanded particle manufacturing condition 1. As a result, the expansion ratio of the pre-expanded particles was 31 times.

Further, the fusion rate of the pre-expanded particles is 60%.
The in-mold forming temperature exceeding 60% was measured by the same method as the in-mold forming temperature in which the fusion rate of the pre-expanded particles produced under the pre-expanded particle production condition 1 exceeded 60%. As a result, the in-mold molding temperature at which the fusion rate exceeded 60% was 148 ° C.

In the evaluation of the fusion rate, the molding temperature at the limit of the fusion rate of more than 60% (in this case, 14
The expansion ratio of the foamed molded product at 8 ° C.) was measured by the same method as the method for measuring the expansion ratio of the pre-expanded particles. As a result, the expansion ratio of this foamed molded product was 36 times.

Examples 2 to 4 100 parts by weight of a propylene homopolymer as a polypropylene resin before graft copolymerization, 20 parts by weight of styrene as a vinyl monomer, and α, α'- as a polymerization initiator.
Instead of using 3.5 parts by weight of bis (t-butylperoxy-m-isopropyl) benzene, Table 1 shows polypropylene resin before graft copolymerization, vinyl monomer and polymerization initiator shown in Table 1. Example 1 except used in proportions
Pellets of modified polypropylene resin having the same shape were obtained by the same method.

The peak value of the melting temperature of the propylene resin before the graft copolymerization, the peak value of the melting temperature of the modified polypropylene resin, the weight average molecular weight of the modified polypropylene resin, and the modified polypropylene resin 1 The number of parts by weight of the aromatic graft chain grafted to parts by weight,
The weight average molecular weight of the aromatic vinyl graft chain and the number of aromatic vinyl graft chains were determined by the same method as in Example 1. Table 2 shows the results.

Next, using the modified polypropylene resin pellets, pre-expanded particles were produced in the same manner as in the pre-expanded particle production condition 1 of Example 1 except that the conditions for foaming temperature shown in Table 3 were changed. The expansion ratio of the pre-expanded particles was measured by the same method as in Example 1. The results are shown in Table 3.

Further, the fusion rate of the pre-expanded particles is 60%.
The in-mold molding temperature exceeding the range was determined by the same method as in Example 1. The results are shown in Table 4.

Next, using the pellets of the modified polypropylene resin, the pre-expanded particle production condition 2 of Example 1 was used.
Pre-expanded particles were prepared by the same method as described above. The expansion ratio of the pre-expanded particles was measured by the same method as in Example 1. The results are shown in Table 3.

The fusion rate of the pre-expanded particles was 60%.
The in-mold molding temperature exceeding the range was determined by the same method as in Example 1. The results are shown in Table 4.

Example 5 A modified polypropylene resin pellet obtained by melt extrusion using the same method and the same material as in Example 1 was used.
Using the same melt extruder as in Example 1, melt extrusion was performed again under the same conditions as in Example 1 to obtain modified polypropylene resin pellets.

The peak value of the melting temperature of the propylene resin before the graft copolymerization, the peak value of the melting temperature of the modified polypropylene resin, the weight average molecular weight of the modified polypropylene resin, and the modified polypropylene resin 1 The number of parts by weight of the aromatic graft chain grafted to parts by weight,
The weight average molecular weight of the aromatic vinyl graft chain and the number of aromatic vinyl graft chains were determined by the same method as in Example 1. Table 2 shows the results.

Next, using the modified polypropylene resin pellets, pre-expanded particles were produced in the same manner as in the pre-expanded particle production condition 1 of Example 1 except that the expansion temperature shown in Table 3 was changed. The expansion ratio of the pre-expanded particles was measured by the same method as in Example 1. The results are shown in Table 3.

The fusion rate of the pre-expanded particles was 60%.
The in-mold molding temperature exceeding the range was determined by the same method as in Example 1. The results are shown in Table 4.

Next, the same method as the pre-expanded particle production condition 2 of Example 1 was used except that the modified polypropylene resin pellets were used instead of the foaming temperature (set temperature condition of the extruder) shown in Table 2. To produce pre-expanded particles. The expansion ratio of the pre-expanded particles was measured by the same method as in Example 1. The results are shown in Table 3.

The in-mold molding temperature at which the fusion rate of the pre-expanded particles exceeded 60% was determined by the same method as in Example 1. The results are shown in Table 4.

[0136]

[Table 1]

[0137]

[Table 2]

[0138]

[Table 3]

[0139]

[Table 4]

Comparative Example 1 Propylene homopolymer (Noblene D501, manufactured by Sumitomo Chemical Co., Ltd.) was added to styrene and α, α'-bis (t-
Resin pellets having the same shape were obtained by the same method as in Example 1 except that butylperoxy-m-isopropyl) benzene was not added.

The peak value of the melting temperature and the weight average molecular weight of this polypropylene resin were determined by the same method as in the modified polypropylene of Example 1. as a result,
The peak value of the melting temperature was 160 ° C. and the weight average molecular weight was 850000.

Pre-expanded particles were produced using this resin by the same method as the pre-expanded particle production condition 1 of Example 1 except that the foaming temperature was changed to 161 ° C. The expansion ratio of the pre-expanded particles was measured by the same method as the measurement of the expansion ratio of Example 1. As a result, it was 20 times.

Using the pre-expanded particles, at 163 ° C., a foam-molded article was produced by the same method as the method for producing the foam-molded article in the measurement of the fusion rate in Example 1, and the pre-expanded particles were produced by the same method as in Example 1. The fusion rate was measured. As a result, the fusion rate is about 1
It was 0%.

Next, an attempt was made to produce pre-expanded particles by the same method as the pre-expanded particle production condition 2 of Example 1. However, in the production of the pre-expanded particles, there has been a problem in that the foamed resin strand cannot be cut well and the cut surface becomes worn.

Comparative Example 2 100 parts by weight of a propylene homopolymer (Noblene D501, manufactured by Sumitomo Chemical Co., Ltd.) and α, α'-bis (t-butylperoxy-m-isopropyl) benzene (NOF Corporation). Made, perbutyl P, 1 minute half-life temperature 175
C.) 3.5 parts by weight (without styrene)
Others tried to extrude the modified polypropylene resin by melt-extrusion in the same manner as in Example 1 to prepare a strand, but a good strand could not be formed and a resin pellet could not be obtained. .

Comparative Example 3 An attempt was made to prepare a strand by melt-extruding a modified polypropylene resin in the same manner as in Example 1 except that 20 parts by weight of methyl methacrylate was used instead of 20 parts by weight of styrene. However, good strands could not be formed and resin pellets could not be obtained.

Examples 6 to 18 100 parts by weight of a propylene homocopolymer as a polypropylene resin before graft copolymerization, 20 parts by weight of styrene as a vinyl monomer, and α, α'-as a polymerization initiator.
Instead of using 3.5 parts by weight of bis (t-butylperoxy-m-isopropyl) benzene, Table 5 shows polypropylene-based resin, vinyl monomer and polymerization initiator before graft copolymerization shown in Table 5. Pellets of modified polypropylene resin having the same shape were obtained by the same method as in Example 1 except that the pellets were used in the same proportions.

Grafting of peak value of melting temperature of propylene-based resin before graft copolymerization, peak value of melting temperature of modified polypropylene-based resin, weight average molecular weight of modified polypropylene-based resin, 1 part by weight of modified polypropylene-based resin The number of parts by weight of the aromatic graft chains, the weight average molecular weight of the aromatic vinyl graft chains, and the number of aromatic vinyl graft chains were determined in the same manner as in Example 1. Table 6 shows the results.

Next, using the modified polypropylene resin pellets, pre-expanded particles were produced by the same method as in the pre-expanded particle production condition 1 of Example 1 except that the expansion temperature conditions shown in Table 7 were changed. The in-mold molding temperature at which the fusion rate of the pre-expanded particles exceeded 60% was determined by the same method as in Example 1. Table 7 shows the results.

Next, the modified polypropylene resin pellets were used to prepare pre-expanded particles by the same method as the pre-expanded particle manufacturing condition 2 of Example 1. The in-mold molding temperature at which the fusion rate of the pre-expanded particles exceeded 60% was determined by the same method as in Example 1. Table 7 shows the results.

[0151]

[Table 5]

[0152]

[Table 6]

[0153]

[Table 7]

[0154]

[Table 8]

[0155]

[Table 9]

[0156]

[Table 10]

[0157]

[Table 11]

[0158]

The modified polypropylene resin of the present invention is
It has an average of one or more aromatic vinyl graft chains with a weight average molecular weight of 200 or more per molecule, and the peak value of the melting temperature is lower than that of the polypropylene resin before graft copolymerization. When molding pre-expanded particles using this, in-mold molding can be performed at a lower temperature. In addition, the pre-expanded particles can be foamed at a lower temperature.

The modified polypropylene resin is
High rigidity, chemical resistance, impact resistance and heat resistance, which are the characteristics of polypropylene resins, do not fall below the practical range.

The modified polypropylene resin is produced by a relatively easy method of carrying out a graft copolymerization reaction by melt-kneading an aromatic vinyl monomer in a polypropylene resin in the presence of a radical polymerization initiator. sell.

[Brief description of drawings]

FIG. 1 is a DSC of modified polypropylene resin of Example 1.
It is a pattern.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Ojiro 6-31-17 Shioya-machi, Tarumi-ku, Kobe-shi, Hyogo (72) Inventor Taizo Aoyama 4-13-10 Nishihata, Takasago-shi, Hyogo (72) Tomita Shunsei 28-1 Taihatahigashi-cho, Suma-ku, Kobe-shi, Hyogo

Claims (11)

[Claims] 1. A graft copolymer of a polypropylene resin and an aromatic vinyl monomer, wherein the average number of aromatic vinyl graft chains grafted in one graft copolymer molecule is 1 or more. And a modified polypropylene resin in which the weight average molecular weight of the aromatic vinyl graft chain is 200 or more. 2. The peak value of the melting temperature of the modified polypropylene resin is lower by 1 ° C. or more than the peak value of the melting temperature of the polypropylene resin before graft copolymerization.
The modified polypropylene resin described. 3. The peak value of the melting temperature of the modified polypropylene resin is lower by 5 ° C. or more than the peak value of the melting temperature of the polypropylene resin before graft copolymerization.
The modified polypropylene resin described. 4. A graft copolymer of a polypropylene resin and an aromatic vinyl monomer, wherein the average number of grafted aromatic vinyl graft chains in one graft copolymer molecule is 1 or more. And pre-expanded particles composed of a modified polypropylene resin in which the weight average molecular weight of the aromatic vinyl graft chain is 200 or more. 5. The peak value of the melting temperature of the modified polypropylene resin is lower by 1 ° C. or more than the peak value of the melting temperature of the polypropylene resin before graft copolymerization.
Pre-expanded particles as described. 6. The peak value of the melting temperature of the modified polypropylene resin is 5 ° C. or more lower than the peak value of the melting temperature of the polypropylene resin before graft copolymerization.
Pre-expanded particles comprising the modified polypropylene resin described. 7. The pre-expanded particles according to claim 4, 5 or 6, which are obtained by foaming the modified polypropylene resin with or without using a melt extruder and then cutting. 8. The pre-expanded particles according to claim 4, 5 or 6, which are obtained by depressurizing and expanding the modified polypropylene resin. 9. A graft copolymerization method in which a polypropylene resin is melt-kneaded with an aromatic vinyl monomer in the presence of a radical polymerization initiator to graft-copolymerize the aromatic vinyl monomer with the polypropylene resin. A method for producing a modified polypropylene resin, wherein the average number of grafted aromatic vinyl graft chains in one united molecule is 1 or more, and the weight average molecular weight of the aromatic vinyl graft chains is 200 or more. 10. The method for producing a modified polypropylene resin according to claim 9, wherein 0.1 to 10 parts by weight of the radical polymerization initiator is melt-kneaded with 100 parts by weight of the polypropylene resin. 11. A foamed molded product obtained by in-molding the pre-foamed particles according to claim 4, 5, 6, 7 or 8.