JPH11170343A - Modified polypropylene resin hollow molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply provide a hollow molding of uniform thickness by blow molding and others using a simple apparatus, by an easy method, without deteriorating the properties of a polypropylene resin such as rigidity. SOLUTION: A hollow molding consists of a modified polypropylene resin obtained by melt-kneading a mixture of a polypropylene resin, an isoprene monomer, and a radical polymerization initiator. The modified polypropylene resin can be also obtained by melt-kneading a mixture of a polypropylene resin, the isoprene monomer, a vinyl monomer copolymerizable with isoprene, and a radical polymerization initiator. The weight average molecular weight of the polypropylene resin is preferably 50,000-200,000,000 in view of industrial availability, or more preferably 100,000-100,000,000 in terms of the cost. The resin can be mixed with other resins or rubber as required so far as the effects of the product are not deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow molded article made of a modified polypropylene resin and a hollow molded article obtained by extrusion blow molding or injection blow molding.
More specifically, by using a modified polypropylene resin having improved melting properties and excellent workability, it can be manufactured under a wide range of conditions without impairing the characteristics of the polypropylene resin such as rigidity, and has a small uneven thickness. The present invention relates to a hollow molded article and a hollow molded article obtained by extrusion blow molding or injection blow molding of the modified polypropylene resin.

[0002]

2. Description of the Related Art Conventionally, polypropylene has been widely used for various molded articles because of its low cost and excellent physical properties. However, polypropylene has a low viscosity and tension when melted, so that in the case of extrusion blow molding or injection blow molding (hereinafter referred to as blow molding), the drawdown of the parison is large, and the resulting hollow molded body tends to be uneven in thickness. However, it has the disadvantage of low workability.

For the purpose of improving the processability of the polypropylene, polyethylene and the like are generally mechanically mixed, but the effect of improving the processability is insufficient.
A disadvantage is that a large amount of polyethylene is required, and the rigidity of the resulting mixture is reduced. Attempts have been made to improve the viscosity and tension at the time of melting by increasing the molecular weight of the polypropylene. However, polypropylene having a large molecular weight has a serious problem that stretchability at the time of melting is low.

In order to improve the processability of the polypropylene, a mixture of a polyolefin, a methacrylate polymer, and a methacrylate-grafted polyolefin obtained by polymerizing a methacrylate monomer in a hydrocarbon solvent in the presence of the polyolefin. Has been attempted to be added to polypropylene (Japanese Patent Application Laid-Open No. 22316/1990), but in order to sufficiently exhibit such processability-improving effects, a large amount of the mixture is required. Is used, there is a problem in terms of manufacturing cost and safety. Further, it is necessary to remove the solvent at the time of mixing the polyolefin, and there is a problem that workability and safety are poor.

Japanese Patent Application Laid-Open No. 62-121704 discloses that a semi-crystalline polypropylene resin having a linear molecular structure is irradiated with radiation in a gas atmosphere adjusted to a specific oxygen concentration. Has proposed a method of increasing the viscosity and tensile strength of the polypropylene resin at the time of melting. The patent publication states that the polypropylene resin modified by this method has a structure in which the polymer molecule has a long-chain branch, and this resin is used in a molding method such as blow molding or extrusion coating molding. It is stated that it is suitable.

[0006] The reason that the polypropylene resin modified by this method is suitable for these molding methods is that the elongational viscosity of the resin measured in a molten state is as follows.
That is, it increases rapidly as the amount of strain increases, that is, when the resin is subjected to tensile deformation in a molten state, the elongational viscosity increases as the elongational strain increases,
It is pointed out that the elongational viscosity sharply increases after reaching a specific elongational strain value.

However, when the polypropylene resin is modified by this method, it is inevitable that a large-scale apparatus is used and the structure of the apparatus is complicated in order to utilize radiation. In addition, in the irradiation step, in order to prevent decomposition and gelation of the propylene-based resin and stably produce the product, it is necessary to strictly control the irradiation amount of the radiation and the oxygen concentration of the atmosphere gas. Further, since it is necessary to strictly control the production conditions in this way, it has not been easy to give a variation to the physical properties of the target modified polypropylene resin composition.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to use a simple apparatus and a simple method without impairing the inherent characteristics of a polypropylene resin such as rigidity, and by using blow molding or the like to reduce the thickness of the hollow resin. It is to provide a compact easily.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a modified resin obtained by melt-kneading a polypropylene resin, an isoprene monomer and a radical polymerization initiator has been obtained. When using polypropylene resin,
Since the drawdown of the parison was small during blow molding, it was finally found that a hollow molded body with less uneven thickness could be easily produced, and the present invention was completed.

That is, the present invention relates to a hollow molded article made of a modified polypropylene resin obtained by melt-kneading a polypropylene resin, an isoprene monomer and a radical polymerization initiator. Further, the present invention relates to a hollow molded article obtained by subjecting the modified polypropylene resin to extrusion blow molding or injection blow molding.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The modified polypropylene resin of the present invention is obtained by melt-kneading a polypropylene resin, an isoprene monomer and a radical polymerization initiator, and drawdown during melting hardly occurs. The blow moldability is remarkably improved. The modified polypropylene resin used in the present invention comprises a polypropylene resin (hereinafter, this polypropylene resin may be referred to as “raw material polypropylene resin”), an isoprene monomer and a radical polymerization initiator. It is obtained by kneading under the melting temperature.

As the raw material polypropylene resin,
Crystalline polymers such as propylene homopolymers, block copolymers of propylene and other monomers or random copolymers of propylene and other monomers,
From the viewpoint of high rigidity and low cost, the polypropylene homopolymer is preferable, and from the viewpoint of high rigidity and high impact resistance, a block copolymer of the propylene and another monomer is preferable. . When the raw material polypropylene-based resin is a block copolymer of propylene and other monomers or a random copolymer of propylene and other monomers, high crystallinity, which is characteristic of polypropylene-based resins, high From the viewpoint of maintaining rigidity and good chemical resistance, the content of the propylene monomer component is preferably 75% by weight or more of the whole,
It is more preferable that the content be not less than weight%.

In the raw material polypropylene resin,
As other monomers copolymerizable with propylene, one or more selected from the group consisting of ethylene, α-olefin, cyclic olefin, diene monomer and vinyl monomer Monomers. Of these monomers, ethylene or butene-1 is preferred because it is inexpensive.

The molecular weight (weight average molecular weight) of the raw material polypropylene resin is preferably in the range of 50,000 to 2,000,000 from the viewpoint of industrial availability, and from 100,000 to 2,000,000 from the viewpoint of low cost. More preferably, it is within the range of 1,000,000. If necessary, another resin or rubber may be added to the raw material polypropylene-based resin as long as the effects of the present invention are not impaired. Examples of the other resin or rubber include polyethylene;
Polybutene-1, polyisobutene, polypentene-1,
Polyα-olefins such as polymethylpentene-1; ethylene / propylene copolymers having an propylene content of less than 75% by weight, ethylene / butene-1 copolymers, and propylene / butene having a propylene content of less than 75% by weight. Ethylene or α-olefin / α-olefin copolymers such as 1 copolymer; ethylene or α-olefins such as ethylene / propylene / 5-ethylidene-2-norbornene copolymer having a propylene content of less than 75% by weight; α
-Olefin / diene monomer copolymer; ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / methacrylic 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 / vinyl monomer copolymer such as ethylene / glycidyl methacrylate copolymer; polydiene copolymer such as polybutadiene and polyisoprene; vinyl monomer / diene copolymer such as styrene / butadiene / styrene block copolymer Monomer / vinyl monomer block copolymer; vinyl monomer / diene monomer / vinyl monomer such as acrylonitrile / butadiene / styrene graft copolymer, methyl methacrylate / butadiene / styrene graft copolymer Graft copolymer; polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyvinyl acetate,
Vinyl polymers such as polyethyl acrylate, polybutyl acrylate, polymethyl methacrylate, and polystyrene;
Vinyl chloride / acrylonitrile copolymer, vinyl chloride /
Examples include vinyl copolymers such as vinyl acetate copolymers, acrylonitrile / styrene copolymers, and methyl methacrylate / styrene copolymers.

The amount of the other resin or rubber to be added to the starting polypropylene resin depends on the type of the resin or the type of rubber, and may be within the range that does not impair the effects of the present invention as described above. But usually
It is preferably about 25% by weight or less. The modified polypropylene resin of the present invention is produced by melt-kneading a polypropylene resin, an isoprene monomer, another vinyl monomer copolymerizable with the isoprene monomer, and a radical polymerization initiator. Is also good.

Other vinyl monomers copolymerizable with the isoprene monomer include, for example, vinyl chloride; vinylidene chloride; styrene; acrylonitrile; methacrylonitrile; acrylamide; methacrylamide; vinyl acetate; Acid; maleic acid; maleic anhydride; metal acrylate; metal methacrylate; acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, stearyl acrylate, glycyl acrylate; methyl methacrylate, methacrylic acid Examples include methacrylates such as ethyl, butyl methacrylate, stearyl methacrylate, and glycidyl methacrylate.

When the isoprene monomer and another vinyl monomer copolymerizable with the isoprene monomer are used in combination, the amount of the other vinyl monomer copolymerizable with the isoprene monomer is reduced. The amount is preferably 100 parts by weight or less, more preferably 75 parts by weight or less on average with respect to 100 parts by weight of the isoprene monomer. When the amount of the other vinyl monomer copolymerizable with the isoprene monomer exceeds the above range, the viscosity of the obtained modified polypropylene resin is significantly reduced, and the drawdown of the parison increases during blow molding. There is a case.

The amount of the isoprene monomer to be melt-kneaded is preferably 0.1 to 30 parts by weight, and more preferably 1 to 10 parts by weight, based on 100 parts by weight of the starting polypropylene resin.
More preferably, it is part by weight. When the amount of the isoprene monomer is less than the above range, there is a case where the drawdown of the parison becomes large during blow molding,
On the other hand, if it exceeds the above range, the heat resistance and rigidity, which are characteristics of the polypropylene resin, may be impaired.

The radical polymerization initiator generally includes a peroxide or an azo compound. As the radical polymerization initiator, one or more kinds of organic peroxides such as ketone peroxide, peroxyketal, hydroperoxide, dialkyl peroxide, diacyl peroxide, peroxydicarbonate, peroxyester, and the like are used. can give. Of these,
Particularly, those having a high hydrogen abstracting ability are preferable. Examples of such a radical polymerization initiator include 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane and 1,1-bis ( t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-
Peroxyketals such as butylperoxy) valerate and 2,2-bis (t-butylperoxy) butane; dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, α, α'-bis (t-butylperoxy-m-isopropyl) benzene, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-
Dialkyl peroxides such as butylperoxy) hexyne-3; diacyl peroxides such as benzoyl peroxide; t-butylperoxyoctate;
-Butylperoxyisobutyrate, t-butylperoxylaurate, t-butylperoxy-3,5,5-
Trimethylhexanoate, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate, t-butylperoxybenzoate,
One or more of peroxyesters such as di-t-butylperoxyisophthalate may be used.

When the amount of the radical polymerization initiator added is such that the blow moldability of the modified polypropylene-based resin is good and economical, the starting polypropylene-based resin 1
It is preferably in the range of 0.1 to 10 parts by weight, more preferably in the range of 0.2 to 5 parts by weight, based on 00 parts by weight. Further, if necessary, an antioxidant, a metal deactivator,
Phosphorus-based processing stabilizers, ultraviolet absorbers, ultraviolet stabilizers, fluorescent brighteners, stabilizers such as metal soaps, antacid adsorbents, or crosslinking agents, chain transfer agents, nucleating agents, lubricants, plasticizers, fillers Further, additives such as a reinforcing material, a pigment, a dye, a flame retardant, and an antistatic agent may be added within a range that does not impair the effects of the present invention.

By the presence of a nucleating agent in the modified polypropylene resin, the transparency of the modified polypropylene resin hollow molded article can be improved without impairing the blow moldability. Examples of the nucleating agent include sodium benzoate, bisbenzylidene sorbitol,
Bis (p-methylbenzylidene) sorbitol, bis (p-ethylbenzylidene) sorbitol, sodium 2,2-methylenebis (4,6-di-t-butylphenyl) phosphite, and the like.

The amount of the nucleating agent added is such that the transparency of the hollow body of the modified polypropylene-based resin is sufficiently improved and the economy is economical.
It is preferably 0.01 to 2 parts by weight based on 00 parts by weight. In addition, the presence of an inorganic filler in the modified polypropylene resin improves the rigidity, surface properties, coating properties, printability, etc., of the modified polypropylene resin hollow molded article without impairing blow moldability. can do.

Examples of the inorganic filler include calcium carbonate, talc, glass fiber, magnesium carbonate, mica, kaolin, calcium sulfate, barium sulfate, titanium white, white carbon, carbon black, aluminum hydroxide, magnesium hydroxide and the like. One or more kinds may be mentioned. Of these, calcium carbonate and talc are preferred because they are easily available.
The average particle diameter of the inorganic filler is preferably about 10 μm or less, especially about 5 μm or less, in order to improve the surface properties of the obtained modified polypropylene resin hollow molded article.

The amount of the inorganic filler to be added is sufficiently improved with respect to the rigidity of the modified polypropylene resin hollow molded article and does not impair the surface properties. Preferably 1 to 100 parts by weight, more preferably 5 to 50 parts by weight. The order and method of mixing and melt-kneading these raw material polypropylene resin, isoprene monomer, radical polymerization initiator and other added materials are not particularly limited. For example, raw material polypropylene resin, isoprene monomer The mixture may be melt-kneaded after mixing the raw material, the radical polymerization initiator and other additives added as necessary, or the raw material polypropylene resin, the radical polymerization initiator and other additives added as necessary After the material is melt-kneaded, the isoprene monomer may be melt-kneaded, or after the modified polypropylene resin is obtained by the above-described method, the mixture is melt-kneaded with additives and other resins added as necessary. And the remaining raw polypropylene after modifying a part of the raw polypropylene to form a masterbatch Resin may be melt-kneaded.

The heating temperature at the time of melt-kneading varies depending on the type of the resin and the like, but it is usually from 130 to 400 ° C. that the raw polypropylene resin is sufficiently melted, does not thermally decompose, and is sufficiently thermoformed. It is preferable in that the property can be obtained. The time for melt-kneading (the time after mixing the radical polymerization initiator and the isoprene monomer) is generally 30 seconds to 60 minutes.

Examples of the melt kneading apparatus include kneaders such as a co-kneader, a Banbury mixer, a Brabender, a single-screw extruder, a twin-screw extruder, a twin-screw surface renewer, and a twin-screw multi-disc apparatus. There is a device such as a horizontal stirrer 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 giving an appropriate shear stress. Among these, a single-screw or twin-screw extruder is particularly preferred in terms of productivity.

The method for producing the hollow molded article from the modified polypropylene resin is not particularly limited, and examples thereof include extrusion blow molding, injection blow molding, injection / extrusion blow molding, sheet blow molding, and cold parison molding. Of these, extrusion blow molding or injection blow molding is preferred from the viewpoint of productivity. In the blow molding, if the drawdown of the parison is large, the central part of the parison tends to be thin (necking), which causes uneven wall thickness of the obtained hollow molded body. If the drawdown is further large, blockage occurs and molding is impossible. Becomes

The drawdown of the parison is, for example,
The polypropylene resin was supplied to an extrusion blow molding machine (BM304, J2) manufactured by Placo Co., Ltd.
Extruded from an annular orifice with a diameter of 35 mm
It can be evaluated from the diameter of the thinnest part of the parison when a 50 mm cylindrical parison is molded. The diameter of the parison measured by the above method is at most about 20 mm for a commercially available polypropylene resin, but according to the present invention, a parison that does not neck at all is formed by selecting conditions for modifying the raw material polypropylene resin. It is also possible.

The unevenness of the bottle is, for example,
When the parison is molded into a bottle having a thickness of 1.0 mm in a blow mold having a set capacity of 1800 ml, a position at a height of 20 mm from the bottom of the bottle and a height of 280 m from the bottom
It can be evaluated from the difference in wall thickness at the position m. The difference in wall thickness measured by the above method, in a commercially available polypropylene resin, is affected by the drawdown of the parison, even if small,
According to the present invention, it is possible to produce a bottle having a thickness of about 0.4 mm without uneven thickness.

[0030]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. The blow moldability was determined by the following method.
The polypropylene resin was supplied to an extrusion blow molding machine (BM304 / J2) manufactured by Placo Co., Ltd.
The cylindrical parison was extruded from a 35 mm diameter orifice at 0 ° C. to form a cylindrical parison, which was formed into a bottle in a blow mold having a set capacity of 1800 ml. The height of the bottle is 3
The molding conditions were set so that the thickness was 50 mm and the thickness was 1.0 mm at a position 150 mm above the bottom. <Drawdown of parison> Length of parison 350m
Based on the diameter of the thinnest part of the parison in m, the evaluation was made according to the following criteria.

〇: 25 mm or more ×: less than 25 mm <Positive wall thickness> Height of the molded bottle from the bottom 2
From the difference in wall thickness between the position of 0 mm and the position of a height of 280 mm from the bottom, the following criteria were used to evaluate.

〇: less than 0.3 mm ×: 0.3 mm or more (Example 1) 100 weight of ethylene propylene random copolymer (ethylene content: 3% by weight, melt flow index at 230 ° C .: 0.5 g / 10 minutes) Part and 1,1-
A mixture prepared by stirring and mixing 0.5 parts by weight of bis (t-butylperoxy) -3,3,5-trimethylcyclohexane with a ribbon blender was subjected to a twin-screw extruder (TEX44XCT, manufactured by Nippon Steel Works Co., Ltd.) using a measuring feeder. -38), 1.5 parts by weight of isoprene monomer was supplied from the middle of the extruder using a liquid addition pump, and the mixture was melt-kneaded and melt-extruded in the twin-screw extruder to obtain a modified polypropylene. A resin pellet was obtained.

The twin-screw extruder was of the same-direction twin-screw type, had a screw diameter of 44 mmφ, and had a maximum effective screw length (L / D) of 38. The set temperature of the cylinder part of this twin-screw extruder was 180 ° C. until the injection of isoprene monomer, 200 ° C. after the injection of isoprene, and the screw rotation speed was set at 150 rpm. When the above-mentioned blow moldability evaluation of the obtained modified polypropylene resin was performed, the parison diameter was 3.5 mm, the difference in the wall thickness of the bottle was 0 mm, and the drawdown property and the uneven thickness of the bottle were both evaluated as ○. there were. (Comparative Example 1) The blow moldability of an ethylene propylene random copolymer (ethylene content: 3% by weight, melt flow index at 230 ° C: 0.5 g / 10 minutes) was evaluated in the same manner as in Example 1. The parison diameter is 2.3m
m, the difference in wall thickness between the bottles was 0.4 mm, and both the drawdown property and the uneven wall thickness of the bottle were x. (Examples 2 and 3) Polypropylene resins described in Table 1,
A modified polypropylene resin was obtained and blow moldability was evaluated in the same manner as in PP1, except that the types and amounts of the isoprene monomer and the radical polymerization initiator were used. Table 2 shows the obtained results.

[0034]

[Table 1]

[0035]

[Table 2]

When the modified polypropylene resin in the examples was used, necking hardly occurred due to the small drawdown of the parison. Therefore, the bottle obtained by blow-molding this resin was small in uneven thickness, whereas the bottle obtained by blow molding was comparatively small. When the unmodified ethylene propylene random copolymer shown in No. 1 is used, necking occurs due to a large drawdown, and it can be seen that the obtained bottle also has a large uneven thickness.

[0037]

According to the present invention, the modified polypropylene resin is
Drawdown is less likely to occur during parison molding, and the resulting molded article can be reduced in thickness deviation.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29L 22:00 C08L 23:14

Claims (2)

[Claims] 1. A hollow molded article comprising a modified polypropylene resin obtained by melt-kneading a polypropylene resin, an isoprene monomer and a radical polymerization initiator. 2. The hollow molded article according to claim 1, which is obtained by extrusion blow molding or injection blow molding.