JPS6367802B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a polyolefin resin composition. More specifically, polyolefin and organic peroxide are separately added to the melt-kneaded product.
The present invention relates to a method for producing a composition having excellent moldability, which comprises mixing a crosslinking aid and a necessary organic peroxide and melt-kneading the mixture.

Polyolefin resins are widely used as general-purpose thermoplastic resins for molding various articles. The moldability of a polyolefin resin is determined by the suitability of the melt viscoelastic value of a melt of the resin under shear stress.

For example, for blow molding or sheet molding, low shear stress requires high melt viscosity with high melt elasticity, and high shear stress requires a polymer with low melt viscosity or high flowability. The physical factors governing the melt viscosity of such polymers are primarily the size of the molecular weight, followed by the breadth and narrowness of the molecular weight distribution.
That is, in general, as the molecular weight of polyolefin increases, the melt flow index decreases and the fluidity of the melt decreases. However, even if polyolefins have the same average molecular weight, if the molecular weight distribution is wide or narrow, the fluidity will differ, and those with a wide molecular weight distribution will have high fluidity. This is believed to be because the low molecular weight portion of the polyolefin functions as a diluent or lubricant for the high molecular weight portion in the melt-flowing state.

Based on the above technical knowledge, many proposals have been made to improve the processability of polyolefins. A typical method is to perform multi-stage polymerization during the polymerization of olefins, in which a high molecular weight polyolefin is produced in the first stage, and then a low molecular weight polyolefin is produced in the second and subsequent stages. This is a method for producing polyolefins with a wide molecular weight distribution by adjusting the production amount and average molecular weight of the polymer produced in the first stage, second stage and subsequent stages (Japanese Patent Application Laid-open No. 123637-1989, 56
-84712, 56-70014, 57-185304, 58-
7406 etc.).

Another typical method for producing polyolefins with a wide molecular weight distribution is to mix a high molecular weight polymer and a low molecular weight polymer in advance, for example, in a Henschel mixer (Note: high-speed mixer, trade name), and then extrude the mixture. This is a method of melting and kneading using a machine etc.
57-18737, 58-7439).

Although each of the above two groups of invention proposals has a considerable effect of improving workability, there is still room for improvement in the following points. That is, the former multi-stage polymerization method is suitable for continuous production in large quantities, but is not suitable for individually producing small quantities of various standardized products. Moreover, a considerable amount of substandard polyolefin is produced before and after changing over production types. In the latter method of melt-kneading a mixture of polymers, it is difficult to obtain a low molecular weight polyolefin of any composition. In addition, if the difference in average molecular weight between a low molecular weight product and a high molecular weight product becomes large, it becomes difficult to achieve uniform mixing by melt kneading, and as a result, molded products produced using the melt kneaded product often suffer from sticking eyes, resulting in poor quality molded products. It becomes difficult to obtain.

The inventors of the present invention have conducted intensive research to solve the above-mentioned technical problems related to known techniques. As a result, we divided the polyolefins to be used in the production of polyolefin resin compositions with a wide molecular weight distribution into at least two groups.
One group is kneaded and melted with the necessary organic peroxide to reduce the average molecular weight to the desired melt flow index, and the other group is kneaded and melted with the necessary organic peroxide to reduce the average molecular weight to the desired melt flow index. The present invention was completed knowing that by mixing and melt-kneading, all the technical problems related to the above-mentioned known techniques can be solved. As is clear from the above description, the purpose of the present invention is to eliminate the generation of inferior products due to mass production, to be able to carry out both mass production and small quantity production efficiently, and to constantly produce low degree of polymerization polyolefin with the required composition. It is an object of the present invention to provide a method for producing a polyolefin resin composition that does not require preparation and can effectively perform melt-kneading. Another object is to provide a polyolefin resin composition with good moldability and good physical properties of molded articles.

The present invention has the following main configuration (1) and embodiment configurations (2) to (6).

(1) A composition obtained by melt-kneading a mixture of a polyolefin and a necessary organic peroxide, and then melt-kneading a composition obtained by separately mixing a polyolefin, a crosslinking aid, and a necessary organic peroxide. A method for producing a polyolefin resin composition.

(2) Using an extruder with two or more raw material input ports,
The mixture of polyolefin and organic peroxide is charged into the first to last input ports counting from the one farthest from the discharge port, and the polyolefin and organic peroxide mixture are similarly poured into the second to last input ports. 2. The manufacturing method according to item 1 above, wherein a composition containing a crosslinking auxiliary agent and a necessary organic peroxide is added.

(3) As polyolefins, propylene homopolymer, atactic polypropylene, ethylene/α-olefin random copolymer, ethylene/α-olefin block copolymer,
The manufacturing method according to item 1 above, using one or more selected from ethylene/propylene rubber or polyethylene.

(4) α-olefin is propylene, butene-
1, pentene-1, hexene-1, 4-methylpentene-1, heptene-1, octene-1, or decene-1.

(5) As organic peroxides, dicumyl peroxide, 2,5-dimethyl 2,5-di(t-butylperoxy)hexane, 2,5-dimethyl 2,
5-di(t-butylperoxy)hexyne 3,
1,3-bis(t-butylperoxy)isopropylbenzene, 1,1,4,4,7,7-hexamethylcyclo4,7-diperoxynonane, cumene hydroperoxide, or cumylperoxytrimethylsilane, etc. The manufacturing method according to item 1 above, which uses one or more compounds selected from.

(6) As a crosslinking aid, liquid polybutadiene, triallyl cyanurate, triallyl isocyanurate, (di)ethylene glycol (di)methacrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, Divinylbenzene, diaryl phthalate, divinylpyridine, vinyltoluene, ethylvinylbenzene, styrene monomer, quinone dioxime, p-nitrosophenol, N,N'-m-phenylene bismaleimide,
Vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane or γ-
The manufacturing method according to item 1 above, which uses one or more compounds selected from aminopropyltriethoxysilane.

The structure and effects of the present invention will be explained in detail below.

(a) Polyolefin used in the present invention: One type or a mixture of two or more types of polyolefins including the polyolefins described in (3) above are used.

Homopolymers include polyethylene (low, medium,
high density product), polypropylene, polybutene-1,
Polypentene-1, polyhexene-1, poly-4
-Methylpentene-1, polyheptene-1, polyoctene-1, polydecene-1, etc.
Furthermore, atactic polypropylene can also be used on the condition that it is mixed with the ethylene and α-olefin copolymer described below.

The copolymer is a random or block copolymer of ethylene and other α-olefins. The α-olefins include propylene,
Butene-1, Pentene-1, Hexene-1, 4-
Methylpentene-1, heptene-1, octene-
1 or decene-1. Examples of other copolymers include ethylene vinyl acetate copolymer, ethylene propylene rubber, and ethylene propylene diene rubber.

(b) Organic peroxide used in the present invention: A predetermined amount of the organic peroxide as described in (5) above is mixed with polyolefin. Any organic peroxide can be used as long as it substantially thermally decomposes to generate radicals at a temperature equal to or higher than the polyolefin flow initiation temperature used in the present invention. Specific examples include dicumyl peroxide, 2,5-dimethyl 2,5-di(t-butylperoxy)hexane, 2,5-dimethyl 2,5
-di(t-butylperoxy)hexyne 3, 1,
Examples include 3-bis(t-butylperoxy)isopropylbenzene, 1,1,4,4,7,7-hexamethylcyclo4,7-diperoxynonane, cumene hydroperoxide, and cumylperoxytrimethyl.

C. Crosslinking aid used in the present invention: A predetermined amount of the crosslinking aid as described in (6) above is mixed with the polyolefin. The crosslinking aid can be used as long as it crosslinks the polyolefin used in the present invention at a temperature higher than the flow temperature of the polyolefin. Such crosslinking aids include liquid polybutadiene, polyfunctional monomers, monofunctional monomers, oximes, nitroso compounds, maleimide compounds, silane coupling agents, and the like. Specific examples include 1,2-polybutadiene, 1,4-polybutadiene, triallyl cyanurate, triallyl isocyanurate, (di)ethyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri Polyfunctional monomers such as acrylate, pentaerythritol tetraacrylate, divinylbenzene, diaryl phthalate or divinylpyridine, monofunctional monomers such as vinyltoluene, ethylvinylbenzene or styrene monomer, oximes such as quinone dioxime, benzoquinone oxime etc. , p-nitrosophenol or a nitroso compound or maleimide compound such as N,N′-m-phenylenebismaleimide, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane or γ-
Examples include silane coupling agents such as aminopropyltriethoxysilane.

D. Melt-kneaded product produced in the first stage: The polyolefin used preferably has the same or higher melt index as the polyolefin used in the second stage described below. The reason for this is that in many cases, the raw material polyolefin in the melt-kneaded material used in this process is decomposed by the action of organic peroxides and the melt index increases, and the melt index with the polyolefin supplied in the next step increases. This is because it is prepared to increase the difference in thickness and facilitate uniform mixing and kneading. Therefore, it is disadvantageous to use a polyolefin having a lower melt index than the polyolefin supplied in the second stage because it requires the application of more severe decomposition conditions (molecular weight reduction due to thermal decomposition). . Of course, different types of polyolefins are the first
When the polyolefin is used separately in the second stage and the second stage, it is preferable to use a polyolefin with a larger melt index at the melt-kneading temperature in the first stage, regardless of its average molecular weight.

The conditions for melt-kneading are, for example, when using an extruder with two raw material input ports as shown in the figure (cross-sectional view), pour the mixture of polyolefin and organic peroxide into the input port A, which is farther from the die D. Then, melt kneading and constant thermal deterioration proceed between temperature measurement points C ₁ to C ₃ . The mixing ratio of the organic peroxide is about 0.00 to 10.00 WT%, preferably about 0.1 to 5 WT%, based on the weight of the polyolefin. It is also possible to employ a method using shear force or other thermal degradation methods without using peroxide or in place of organic peroxide. The kneading temperature for _C1 to _C3 points varies depending on the polyolefin used, but is approximately 170 to 250℃.
That's about it.

When using the same polyolefin as used in the second stage, the melt index is preferably increased at this stage to 20 to 100 times that before melt-kneading. Of course, in this step, pellets having the desired melt index may be obtained by using an extruder separate from the second stage. In the case of the figure, the time required for the first stage is about 10 seconds to 3 minutes, preferably about 20 seconds to 1 minute. Although most of the organic peroxide used is decomposed, conditions (mixing ratio, kneading temperature, residence time) may be adopted so that some undecomposed part is decomposed in the second stage.

(e) Melt-kneaded product produced in the second step: In this step, the melt-kneaded product produced in the first step is added with the following raw materials: a polyolefin, a crosslinking aid, and a necessary organic peroxide. Mix, melt and knead the materials. It is preferable that these raw materials are uniformly mixed in solid form beforehand and then supplied to the melt-kneading apparatus. The polyolefin used preferably has the same or lower melt index as the polyolefin used in the first stage described above. The reason for this is as stated in d above.

The conditions for melt-kneading are, for example, when using an extruder as shown in the figure above, the above raw material mixture is charged into the input port B, which is closer to the die D, and the temperature measurement point is
Temperature measurement point C ₁ via input port A between C ₃ and C ₅
The melt-kneaded product produced in the first step is melt-kneaded between ~C ₃ and subjected to a certain crosslinking reaction and a certain degradation.

The mixing ratio of the crosslinking aid in the above raw material mixture is 0.1 to 15wt in weight ratio to the polyolefin.
%, the required mixing ratio of organic peroxide is 0.00~
If the organic peroxide mixed in the first stage and undecomposed in the first stage can be used at around 0.1 WT%, no organic peroxide is used. The kneading temperature at _C3 to _C5 points is about 170 to 230°C. At this stage, the above-mentioned crosslinking aid acts on the melt-kneaded polyolefin to improve the melt viscoelasticity of the melt-kneaded product. When using the same polyolefin used in the first stage, the melt index value of the first stage is usually 20 to 100 times higher than that before melt-kneading due to thermal degradation, but in the second stage The feeds preferably undergo no thermal degradation and both are homogeneously mixed in the second stage. One of the reasons for this is thought to be that the former is a molten substance, and the latter maintains a solid or semi-molten state immediately after being supplied until it is appropriately dispersed within the molten substance. During this time, the polyolefins supplied in the second stage have the effect of further widening the molecular weight distribution by bonding the polyolefins together with each other by the crosslinking aid and increasing the molecular weight.

In the embodiment using the extruder shown in the figure, the low boiling point substances generated by the decomposition of organic peroxide generated at each stage are removed from the exhaust port E installed at the upper part near the discharge port D.
Gaseous substances in the melt-kneaded material are removed by suction by a vacuum system (not shown) connected to the melt-kneaded material.

Of course, it is also possible to have three or more raw material input ports as an extruder. In that case, at least the input port farthest from the discharge port D is charged with only the mixture of the first stage described above, and conversely, the input port closest to the discharge port D is charged with only the mixture of the second stage described above. Make sure to input the following. By charging any of the mixtures at any of the stages described above or a mixture thereof into the intermediate charging port, it is possible to optimize the mixing and kneading conditions. Further, the supply amounts in the first stage and the second stage are adjusted so that the MFR of the composition obtained from the discharge port D is 0.5 to 100.

In another embodiment of the invention, two or more extruders are used, the first extruder performs the melt kneading and thermal degradation of the first stage raw material mixture, and the resulting melt or pellets are Supply to the second and subsequent extruders,
In these extruders, the intermediate product obtained in the first extruder is supplied to the second and subsequent extruders together with the raw material mixture of the second stage to produce the polyolefin resin composition according to the method of the present invention. It is also possible to do so.

The polyolefin resin composition produced as described above has the following effects as compared with known corresponding compositions. That is, due to the lubricant function of the low molecular weight polyolefin, fluidity during melt processing is extremely good. In addition, some of the polyolefin molecules whose molecular weight has been made high by the crosslinking aid act as a nucleating agent, and when the composition solidifies from a molten state, the crystallization rate is significantly accelerated, resulting in high rigidity and tensile strength. And a molded product with high surface strength can be obtained. Furthermore, since it exhibits high elasticity and high melt tension as properties when melted, it exhibits excellent processability as a polyolefin for blow molding or foam molding.

The present invention will be explained below with reference to Examples.

Example 1 Melt flow index (Note: 230℃, load 2.16Kg, 10 minutes flow g) as a composition for the first stage.
20 polypropylene (propylene homopolymer) powder, 0.4% by weight of 1,3-bis(t-butylperoxyisopropyl)benzene, and 0.1% by weight of 2,6-di-t-butyl- p-
Cresol, 0.05% by weight of tetrakis[methylene (3,5-di-t-butyl-4-hydroxy-hydrocinnamate) methane] and 0.1% by weight of calcium stearate were added, and Henschel mixer [trade name, Mitsui Miike] was added. (manufactured by Seisakusho Co., Ltd.) and was thoroughly mixed and stirred, and the mixture was introduced into the extruder from section A in the figure.

Next, as a composition for the second stage,
Polypropylene (homopolymer) powder with MFR 0.5, 2% by weight of liquid 1,2-polybutadiene (crosslinking aid), 1% by weight of trimethylolpropane triacrylate (same as above) and those used in the first step. The same type and amount of stabilizer was added, mixed and stirred in the same manner, and charged into the extruder from section B in the figure. As the extruder, PCM-45 manufactured by Ikegai Tekko Co., Ltd. was used.

The composition for each stage is fed the same weight/hour;
The temperature conditions inside the machine are: ₁ part C: 170°C, ₂ parts C: 240°C,
_C3 part: 150°C and _C4 to D part: 200°C. D
The molten material extruded from the die was solidified by cooling with water and then cut into pellets. The MFR of this pellet was 1.8. The melt viscosity of this pellet was measured using a Koka type flow tester manufactured by Shimadzu Corporation. i.e. melting temperature 230℃,
The melt viscosity at a shear rate of 1000 sec ^-1 was 110 poise.

In addition, using the above pellets, JIS K6758-
The mechanical strength of the molded product was measured using test pieces manufactured in accordance with 1981. As a result, the tensile strength is 398
Kg/cm ² , heat distortion temperature of 130° C., and Rockwell hardness of 105.

Comparative Example 1 The physical properties of commercially available polypropylene (propylene homopolymer, manufactured by Chitsuso Corporation, A5012) pellets having an MFR of 1.8 were measured under the same conditions as in Example 1. As a result, the melt viscosity was 1760 poise, and the tensile strength was 335 kg/
^cm2 , heat distortion temperature 112℃ and Rockwell hardness 98
It was hot.

Example 2 First stage composition with MFR 8.0, ethylene and butene-1 contents of 2.5 and 1, respectively.
4.5% by weight propylene ethylene butene-1
An organic peroxide and a stabilizer were added to and mixed with the random copolymer powder in the same manner as in Example 1, and the mixture was charged into section A of the extruder.

Next, as a composition for the second stage, the above-mentioned random copolymer, 1.5% by weight of 1,2-polybutadiene, 0.5% by weight of trimethylolpropane triacrylate (all of the above are crosslinking coagents), and the second stage of Example 1 were added. The same kind and amount of stabilizer as that used was added and mixed in the same manner, and the mixture was charged from part B of the extruder.

The MFR of the pellets obtained was 80 under the same melt-kneading and extrusion conditions as in Example 1.

The melt tension of this pellet was measured using a melt tension tester manufactured by Toyo Seiki Co., Ltd. (Note: The die used was L/D=40/2, the extrusion speed of the piston was 10 mm/min, and the temperature was 190° C.). The tension value obtained was 0.50 g.

Comparative Example 2 The same polypropylene random copolymer used in Example 2 was treated with the same organic peroxide.
0.07% by weight of the same amount of stabilizer was added and mixed and charged from part B of the extruder. The pellets obtained under the same melt-kneading and extrusion conditions as in Example 1
MFR was 82.

The melt tension of this pellet was measured in the same manner as in Example 2. The tension value obtained was 0.15 g.

[Brief explanation of drawings]

The figure is a cross-sectional flow sheet of the extruder used in the present invention (however, the screw is not a cross-section).

Claims (1)

[Claims] 1. A composition obtained by separately mixing a polyolefin, a crosslinking aid, and a necessary organic peroxide into a melt-kneaded product obtained by melt-kneading a mixture of a polyolefin and a necessary organic peroxide. A method for producing a polyolefin resin composition. 2 Using an extruder with two or more raw material input ports,
The mixture of polyolefin and organic peroxide is charged into the first to last input ports counting from the one farthest from the discharge port, and the polyolefin and organic peroxide mixture are similarly poured into the second to last input ports. The manufacturing method according to claim 1, wherein a composition containing a crosslinking aid and a necessary organic peroxide is added. 3. A patent claim that uses one or more polyolefins selected from propylene homopolymer, atactic polypropylene, ethylene/α-olefin random copolymer, ethylene/α-olefin block copolymer, ethylene/propylene rubber, or polyethylene. The manufacturing method according to item 1. 4 α-olefin is propylene, butene-
1, pentene-1, hexene-1, 4-methylpentene-1, heptene-1, octene-1, or decene-1. . 5 Dicumyl peroxide, 2,5-dimethyl 2,5-di(t-butylperoxy)hexane, 2,5-dimethyl 2,5- as organic peroxides
Di(t-butylperoxy)hexyne 3,1,3
- selected from bis(t-butylperoxy)isopropylbenzene, 1,1,4,4,7,7-hexamethylcyclo4,7-diperoxynonane, cumene hydroperoxide or cumylperoxytrimethylsilane, etc. A method according to claim 1, which uses one or more compounds. 6 As a crosslinking aid, liquid polybutadiene, triallyl cyanurate, triallyl isocyanurate, (di)ethylene glycol (di)methacrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate,
Divinylbenzene, diarylphthalate, divinylpyridine, vinyltoluene, ethylvinylbenzene, styrene monomer, quinone dioxime,
Patents using one or more compounds selected from p-nitrosophenol, N,N'-m-phenylenebismaleimide, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane or γ-aminopropyltriethoxysilane The manufacturing method according to claim 1.