JPH07171869A - Injection molding method for polypropylene resin composition and molded form obtained thereby - Google Patents

Abstract

PURPOSE:To improve transparency, surface gloss and molding processability by injection molding polypropylene resin composition containing specific pts.wt. of syndiotactic polypropylene and specific range pts.wt. of isotactic polypropylene by using molds at a specific temperature. CONSTITUTION:Polypropylene resin composition containing 5-95 pts.wt. of syndiotactic polypropylene and 95-5 pts.wt. of isotactic polypropylene is injection molded by using molds at -5-45 deg.C. A gross value measured at an incident angle of about 60 deg. obtained thereby is injection molded forms of about 88 or more. Thus, its molding processability is much excellent as compared with that of sole syndiotactic polypropylene and easily processed. Much higher transparency and surface glass as compared with those of an injection molded form obtained from a conventional isotactic polypropylene are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injection molding a polypropylene resin composition having excellent transparency and surface gloss, and an injection molded article obtained by the method.

[0002]

2. Description of the Related Art Generally, isotactic polypropylene is widely used for various purposes because it is inexpensive, has excellent mechanical properties, heat resistance, hygienic compatibility, water vapor permeation resistance and the like and has a good appearance of molded articles. .

On the other hand, in recent years, a syndiotactic pentad fraction of 0.7 was obtained by a catalyst composed of a transition metal catalyst having an asymmetric ligand and aluminoxane according to JA Ewen et al.
It was discovered that a polypropylene having a high tacticity of more than 10 can be obtained. (J.Am.Chem.Soc., 1988,11
0,6255-6256). This syndiotactic polypropylene has much higher transparency and surface gloss than conventional isotactic polypropylene, and is also excellent in flexibility, so new applications that could not be applied with conventional isotactic polypropylene are expected. However, it has not been industrially produced due to problems in processability.

[0004]

Isotactic polypropylene is used in various applications because of its excellent properties. Various types of isotactic polypropylene have been used. Among them, crystalline isotactic ethylene-propylene random copolymers, in particular, have relatively good transparency and surface gloss. Although used for etc. However, its transparency and surface gloss are not sufficient, and further improvement has been desired.

In injection molding of isotactic polypropylene, in order to obtain a molded article having good transparency, it is preferable to cool the molten material as soon as possible after putting it in the mold, but to lower the mold temperature to perform injection. When molded, the obtained molded product has a shape such as warpage and a defective appearance, so that the desired molded product cannot be obtained. Therefore, usually, the transparency is slightly sacrificed, and the mold is heated and molded at about 50 to 60 ° C. to obtain a molded product having no shape such as warpage or a defective appearance.

On the other hand, syndiotactic polypropylene has a slower crystallization rate and lower crystallinity than isotactic polypropylene, so that the molded product has relatively low rigidity and slightly sticky surface. There was a problem that it was difficult to release the mold. An object of the present invention is to provide an injection molding method and an injection molded body of a polypropylene resin composition which are excellent in transparency, surface gloss and molding processability, which solve the above problems.

[0007]

In view of the above problems, the present inventors have earnestly studied a method for obtaining an injection-molded article of a polypropylene resin composition which is excellent in transparency, surface gloss and molding processability. As a result of stacking, a polypropylene resin composition composed of 5 to 95 parts by weight of syndiotactic polypropylene and 95 to 5 parts by weight of isotactic polypropylene was injection-molded using a mold at a temperature of −5 to 45 ° C. to be transparent. It was found that a molded product having extremely excellent properties and surface gloss can be obtained, and the present invention has been completed.

That is, according to the present invention, a polypropylene resin composition comprising 5 to 95 parts by weight of syndiotactic polypropylene and 95 to 5 parts by weight of isotactic polypropylene is injection molded using a mold at a temperature of -5 to 45 ° C. And a gloss value measured at an incident angle of 60 ° obtained by the injection molding method is 88.
The above is an injection molded body.

The catalyst for producing syndiotactic polypropylene in the present invention is, for example, JP-A-2-4.
No. 1303, No. 2-41305, No. 2-274703, No. 2-274704, No. 3-179005 (corresponding to USP 5,155,
No. 080,5,225,500), JP-A-3-179006 and JP-A-4-69394, a catalyst comprising a cross-linked transition metal compound having asymmetric ligands and a cocatalyst. However, any catalyst having a different structure can be used as long as it can produce polypropylene having a syndiotactic pentad fraction of 0.7 or more as measured by ¹³ C-NMR. Any of a slurry polymerization method, a bulk polymerization method, and a gas phase polymerization method can be used.

The syndiotactic polypropylene used in the present invention may be a propylene homopolymer having a syndiotactic structure and / or a copolymer of propylene and ethylene or an α-olefin, and further, olefins such as cyclopentene and norbornene and hexadiene. Copolymers containing small amounts of dienes, such as, octadiene, decadiene, dicyclopentadiene, 5-ethylidene-2-norbornene can also be used. Such a copolymer can be obtained by copolymerizing propylene with a small amount of a comonomer in the presence of a known catalyst which gives the poly-α-olefin having good syndiotacticity.

The α-olefin used in the present invention is an α-olefin having 4 to 25 carbon atoms, for example, 1
-Butene, 1-hexene, 1-pentene, 1-decene,
1-Hexadecene and the like are exemplified, and two or more of these or ethylene can also be used.

The syndiotactic propylene homopolymer used in the present invention is a syndiotactic pen which appears at about 20.2 ppm based on tetramethylsilane when measured by ¹³ C-NMR in trichlorobenzene at 135 ° C. The peak of the methyl group attributed to the tad structure is calculated with respect to the sum of the peaks of all the methyl groups (method described in USP 4,892,851), and the syndiotactic pentad fraction is preferably 0.7 or more, particularly preferably Has a value of 0.75 or more. When the syndiotactic propylene copolymer is used in the present invention, the intensity of the peak appearing at about 20.2 ppm in the ¹³ C-NMR measured in the same manner is calculated by the ratio to the peak attributed to the methyl group of all propylene. The syndiotactic pentad fraction of the propylene chain is preferably 0.3 or more, particularly preferably 0.5 or more.

The molecular weight of syndiotactic polypropylene is 0.1 to 10 dl / g, preferably 0.5 to 10 as an intrinsic viscosity measured in a tetralin solution at 135 ° C.
The range of 5.0 dl / g and MFI (melt flow index: ASTM D-1238) are 0.1 to 100.

The isotactic polypropylene used in the present invention may be any of known propylene homopolymers, propylene-ethylene block copolymers and crystalline propylene-ethylene random copolymers which are commercially available. Among them, particularly by using a crystalline propylene-ethylene random copolymer or a polypropylene homopolymer, an injection-molded article having excellent transparency can be obtained. When the copolymer is important for processability, it is recommended to use poropylene homopolymer.

The crystalline propylene-ethylene random copolymer having an isotactic structure has an ethylene content of 1 to 5
%, preferably 2 to 4 wt% is preferably used. In addition, for example, Japanese Patent Laid-Open No. 61-13031
Isotactic polypropylene produced by using a catalyst containing a so-called metallocene compound as a main component, such as those described in JP-A No. 4 and JP-A No. 3-12406, can also be used.

The molecular weight of the added isotactic polypropylene has a limiting viscosity of 0.1 to 10 dl / g, preferably 0.
5 to 5.0 dl / g, MFI (melt flow index: ASTM D-1238) is 0.1 to 100
It is preferred that the MFI is usually close to that of the syndiotactic polypropylene used.

The melting temperature of the resin during molding is 160 to 26.
The range of 0 ° C., the temperature at which normal isotactic polypropylene is run, is selected. At this time, the melting temperature of the resin is set according to the MFI of the main component. The MFI of isotactic polypropylene or syndiotactic polypropylene added in a small amount is 0.5 of the MFI of the main component polypropylene so that it does not cause such things as spots.
Double or more, preferably equivalent or more are used.

The mixing ratio of syndiotactic polypropylene and isotactic polypropylene is 5 to 95 parts by weight of syndiotactic polypropylene, and a polypropylene resin composition comprising 95 to 5 parts by weight of isotactic polypropylene can be used and the desired molding can be performed. Depending on the physical properties of the body, for example, when importance is attached to transparency, it may be appropriately selected so as to increase the mixing ratio of syndiotactic polypropylene. In order to improve the processability of syndiotactic polypropylene, the proportion of syndiotactic polypropylene in the polypropylene resin composition is 95 to 50 parts by weight, preferably 90 to 60 parts by weight, more preferably 85 to 65 parts by weight. In addition, in order to improve the transparency and gloss of isotactic polypropylene, the proportion of isotactic polypropylene is 95 to 50 parts by weight, preferably 90 to 60 parts by weight, and more preferably 85 to 65 parts by weight. It can be selected as appropriate.

If necessary, additives such as antiblocking agents, lubricants, crystal nucleating agents, ultraviolet absorbers, heat stabilizers, weather resistance stabilizers, radiation resistance agents, pigments and dyes are added to the resin composition of the present invention. You may.

Further, in the method of the present invention, if necessary, ethylene-propylene copolymer rubber, ethylene-propylene-diene copolymer rubber, ethylene-butene copolymer rubber, propylene-butene copolymer rubber, styrene. -Various elastomers such as diene block copolymer rubber and its hydrogenated rubber, and resins such as low density polyethylene, high density polyethylene and linear low density polyethylene may be added to improve physical properties such as impact resistance. .

The resin composition of the present invention is prepared by mixing syndiotactic polypropylene, isotactic polypropylene and, if necessary, known stabilizers and additives with a mixer such as a Henschel mixer and then melt-kneading with an extruder. It can be produced by a method of granulating, a method of melt-kneading with a roll, a Banbury mixer, a pressure kneader, a Brabender or the like. Further, the syndiotactic polypropylene and the isotactic polypropylene may be individually granulated by an extruder or the like, and the pellets may be blended and used at the time of molding.

By blending syndiotactic polypropylene and isotactic polypropylene as in the present invention, the crystallization rate of syndiotactic polypropylene is remarkably increased and the moldability is improved.
In the injection-molded article of the present invention, after the pellets of the resin composition of the present invention are produced, the pellets are subjected to a mold temperature of -5 to 45 ° C or less, preferably 5 to 40 ° C or less, more preferably 5 to 3 ° C.
It can be easily manufactured by injection molding at 5 ° C, most preferably 5 to 25 ° C. As a result, it is possible to obtain an injection-molded article having excellent transparency without causing the shape and the appearance defect such as warpage as in the case of isotactic polypropylene. In other molding methods, those used for known isotactic polypropylene can be used as they are as an injection molding machine.

When the mold temperature is lower than room temperature, it is preferable to pass dry air around the mold so that dew does not adhere to the mold. Further, by changing the composition ratio of syndiotactic polypropylene and isotactic polypropylene, not only an injection molded article having desired transparency, surface gloss, and mechanical properties can be obtained, but also a resin mainly composed of syndiotactic polypropylene. The injection-molded product of the composition has extremely high transparency and surface gloss as compared with the injection-molded product of the conventional crystalline isotactic ethylene-propylene random copolymer.

Further, the injection-molded article of the present invention has a clear and clear feeling with less whiteness than the injection-molded article of the usual isotactic polypropylene. For example, it can be used as a packaging medical material, food tapper, syringe, etc. Extremely high commercial value.

[0025]

EXAMPLES The following examples are provided for illustrating the present invention further in detail, but the present invention is not limited thereto. The measuring methods in the examples are as follows, and the respective measured values are shown in Table 1. (1) Melt flow index: ASTM D-12
38 (2) Total Haze: ASTM-D-1003 (3) Internal Haze: Mitsui Toatsu Chemical Method (Using a sample in which liquid paraffin and toluene were mixed at a ratio of 1: 1 on both sides of the sample, ASTM was used. -Haze is measured by D-1003.) (4) Gloss: ASTM D-523 (measured at an incident angle of 60 °) (5) Swarf degree: a disk having a diameter of 120 mmφ, a thickness of 2 mm, and a gate aperture of 3 mmφ by injection molding. Form a sample 2
After 4 hours, conditioned at 23 ° C. and sled H ₀ shown in FIG.
And H ₁ and the diameter L of the disk were used to measure the degree of warpage according to the following equation. Degree of warp (%) = 100 (H ₀ + H ₁ ) / 2L Example 1 The inside of a dry 16 liter stainless steel autoclave was replaced with nitrogen, and 10 liters of liquefied propylene was charged therein. To this, 30 ml of a toluene solution of methylaluminoxane (40 mmol of Al, the average degree of polymerization of methylaluminoxane was 20) was charged and stirred for 15 minutes. On the other hand, in parallel, 12.4 mg of diphenylmethylene- (9-fluorenyl) (cyclopentadienyl) zirconium dichloride was dissolved in 15 ml of a toluene solution of methylaluminoxane (20 mmol of Al and the average degree of polymerization of methylaluminoxane was 20) for 15 minutes. After that, the autoclave was charged and hydrogen was added. The temperature was raised to 70 ° C. and polymerization was carried out at the same temperature for 1 hour. 2.3 kg of syndiotactic polypropylene with the autoclave opened
Got This syndiotactic polypropylene has 13
Intrinsic viscosity of 1.39 measured in tetralin solution at 5 ° C
dl / g, melt flow index (hereinafter abbreviated as MFI) 3.2 g / 10 min, peak temperature of crystallization temperature measured by differential scanning calorimetry is 74.6 ° C. ¹³
80 parts by weight of syndiotactic homopolypropylene (H-SPP) having a syndiotactic pentad fraction of 0.787 as determined by C-NMR, and isotactic homopolypropylene (Mitsui Toatsu Chemicals, Inc.)
Manufactured by JHH-G: intrinsic viscosity 1.6 dl / g, MFI
8 g / 10 min) 20 parts by weight, and injection molding machine (manufactured by Toyo Kikai Metal Co., Ltd., PL with a clamping pressure of 80 t, PL
Barrel temperature 21 using ASTAR TI-80G2)
Injection molding was performed at 0 ° C. and a mold temperature of 25 ° C., and cooling was performed for a cooling time of 15 seconds to obtain a sheet having a length of 170 mm, a width of 80 mm, and a thickness of 2 mm. This sheet has high transparency and surface gloss,
No shape or appearance defect such as warpage was observed. The warp degree of the disk mold injection-molded under the same conditions was 0.7%.

Comparative Example 1 Isotactic homopolypropylene, JHH-G, was injection-molded in the same manner as in Example 1. As a result, warpage was generated in the molded product, and a product having the intended shape could not be obtained. Further, the warpage degree of the disk mold injection-molded under the same conditions was 1.8%.

Example 2 Syndiotactic homopolypropylene, H-SPP
80 parts by weight, and crystalline isotactic ethylene-
Propylene random copolymer (manufactured by Mitsui Toatsu Chemicals, Inc.
GFL-G: intrinsic viscosity 1.5 dl / g, MFI 9 g
/ 10 min, ethylene content 3.1 wt%) 20 parts by weight, and injection-molded in the same manner as in Example 1 to obtain a molded product having high transparency and surface gloss, and having a shape and appearance such as warpage. No defects were found. The warp degree of the disk mold injection-molded under the same conditions was 0.6%.

Example 3 Syndiotactic homopolypropylene, H-SPP
20 parts by weight and 80 parts by weight of the crystalline isotactic propylene-ethylene copolymer GFL-G were blended and injection-molded in the same manner as in Example 1. The transparency and surface gloss were high, and no shape such as warpage or poor appearance was observed. The warp degree of the disk mold injection-molded under the same conditions was 1.1%.

Comparative Example 2 A crystalline isotactic ethylene-propylene random copolymer, GFL-G, was injection-molded in the same manner as in Example 1. As a result, warpage was generated in the molded product and a product having the desired shape was obtained. There wasn't. The warp degree of the disk mold injection-molded under the same conditions was 2.0%.

Comparative Example 3 A sheet was obtained by injection molding in the same manner as in Example 1 except that the mold temperature was 50 ° C. The shape and surface gloss were good, but the transparency was inferior to that of Example 1. The warp degree of a disk mold injection-molded under the same conditions is 0.5.
%Met.

Comparative Example 4 Injection-molded in the same manner as in Comparative Example 1 except that the mold temperature was changed to 50 ° C., and a warp-free sheet was obtained, but the transparency was extremely poor. The shape and surface gloss were good, but the transparency was inferior to that of Example 1. The warp degree of the disk mold injection-molded under the same conditions was 1.0%.

Comparative Example 5 The experiment was repeated by using only syndiotactic homopolypropylene and H-SPP alone as polypropylene in the method of Example 1, but when the cooling time of the mold was 15 seconds, the solidification was insufficient and the mold was separated. I couldn't type. Cooling time 10
Some of them could be released at 0 seconds, but could not be completely released.

[0033]

[Table 1]

[0034]

EFFECT OF THE INVENTION As compared with the method for molding the polypropylene resin composition of the present invention and the syndiotactic polypropylene alone, the molding processability is very good and can be easily processed. In addition, the injection-molded article of the present invention has extremely high transparency and surface gloss as compared with the injection-molded article obtained from the conventional isotactic polypropylene, and can be used for various uses which could not be applied to conventional polypropylenes. .

[Brief description of drawings]

FIG. 1 shows a disk obtained by molding for 24 hours at 23 ° C.
It is drawing which shows the warp measuring method for measuring the warp degree of the molded article after the condition adjustment by.

[Explanation of symbols]

In the drawing, H ₀ and H ₁ are the sizes of the warp of the forming disk measured from the horizontal plane at the diagonal position.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norihide Inoue 1-6 Takasago, Takaishi-shi, Osaka Mitsui Toatsu Chemical Co., Ltd.

Claims (10)

[Claims] 1. Syndiotactic polypropylene 5
95 parts by weight, and isotactic polypropylene 9
An injection molding method, characterized in that 5 to 5 parts by weight of a polypropylene resin composition is injection molded using a mold at a temperature of -5 to 45 ° C. 2. The mold temperature is 5 to 45 ° C.
The molding method described. 3. The temperature of the mold is 5 to 35 ° C.
The molding method described. 4. The gloss value measured at an incident angle of 60 ° is 88.
The injection-molded article obtained by the method according to claim 1, which is as described above. 5. The method for molding a polypropylene resin composition according to claim 1, wherein the polypropylene resin composition comprises 60 to 90 parts by weight of syndiotactic polypropylene and 40 to 10 parts by weight of isotactic polypropylene. 6. The method for molding a polypropylene resin composition according to claim 1, wherein the polypropylene resin composition comprises 65 to 85 parts by weight of syndiotactic polypropylene and 35 to 15 parts by weight of isotactic polypropylene. 7. The gloss value measured at an incident angle of 60 ° is 99.
The injection-molded article obtained by the method according to claim 5, which is as described above. 8. The gloss value measured at an incident angle of 60 ° is 99.
The injection-molded article obtained by the method according to claim 6 as described above. 9. The method for molding a polypropylene resin composition according to claim 1, wherein the polypropylene resin composition comprises 10 to 40 parts by weight of syndiotactic polypropylene and 90 to 60 parts by weight of isotactic polypropylene. 10. The gloss value measured at an incident angle of 60 ° is 8
An injection-molded article obtained by the method according to claim 9, which is 8 or more.