JPH08165382A - Transparent polypropylene press-molded sheet excellent in flexibility - Google Patents

Abstract

PURPOSE: To obtain a polypropylene molded sheet that is suitable for soft sheets, good in transparency, and excellent in flexibility and moldability in comparison with usual press-molded sheets of an isotactic polypropylene. CONSTITUTION: This polypropylene press-molded sheet is obtained by press- molding a sheet obtained by calendering or T-die extrusion molding of a polypropylene resin composition consisting of 5 to 30 pts.wt. syndiotactic polypropylene and 95 to 70 pts.wt. ethylene/α-olefin random copolymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene press-formed sheet which is transparent and has excellent flexibility.
Made of polypropylene with good transparency and excellent flexibility, which is obtained by press molding a polypropylene resin composition consisting of syndiotactic polypropylene and ethylene / α-olefin random copolymer elastomer. Press-formed sheet.

[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, etc. and has a good molded product appearance. In particular, a relatively thin film such as a casting film is suitable for various packaging materials because of its excellent transparency and flexibility.

However, in the case of a film having a thickness of more than 100 μm, transparency and flexibility are gradually lost due to the crystallinity of polypropylene, and the thickness is 0.5
In the case of a sheet of mm or more, the flexibility is remarkably reduced and the transparency is lost. Therefore, in the case of a thick sheet such as a press-formed sheet, it is very difficult to obtain a sheet having good transparency and excellent flexibility.

On the other hand, in recent years, a syndiotactic pentad fraction of 0.7 has been reported by JA Ewen et al. Using a transition metal catalyst having an asymmetric ligand and a catalyst comprising aluminoxane.
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 is more flexible than conventional isotactic polypropylene, and is excellent in transparency and surface gloss, so that it is expected to have new uses that cannot be applied to conventional polypropylenes.

[0005]

Syndiotactic polypropylene is more flexible than the isotactic polypropylene and has excellent transparency, and therefore, it is expected to be used as a soft sheet such as a desk mat. It was

However, in the case of a sheet having a thickness of 0.5 mm or more, the flexibility of syndiotactic polypropylene alone is still insufficient, and Japanese Patent Application No. 6-286296 has been proposed as a method of providing this flexibility. However, the flexural modulus defined by ASTM D833 such as soft polyvinyl chloride with a plasticizer added is 70
It was still harder than soft plastics of less than 0 kg / cm ^2, and further improvement was necessary to obtain a flexible and transparent sheet such as a desk mat.

On the other hand, since syndiotactic polypropylene is a crystalline resin, it has a characteristic that the crystallization rate is slow.
2158), it is relatively easy to mold, but T
-In die extrusion molding or the like, winding of the resin around a cooling roll occurs, which makes it extremely difficult to mold as compared to isotactic polypropylene, and is a raw sheet for press molding. It also had a problem of moldability at the stage of manufacturing.

An object of the present invention is to solve the above problems.
It is an object of the present invention to provide a polypropylene press-formed sheet which has extremely excellent flexibility equivalent to the soft plastic defined in STM D833 and has good transparency and moldability.

[0009]

In view of the above-mentioned problems, the present inventors have made earnest studies on a polypropylene press-formed sheet having excellent transparency and flexibility, and as a result, have found that syndiotactic polypropylene and ethylene / α -By further press-molding a sheet obtained by using a blend with an olefin random copolymer elastomer as a raw material, it was found that a press-formed sheet having extremely excellent flexibility and good transparency and moldability can be obtained, The present invention has been completed. That is, the present invention uses a polypropylene resin composition composed of 5 to 30 parts by weight of syndiotactic polypropylene and 95 to 70 parts by weight of an ethylene / α-olefin random copolymer elastomer by calendar molding or T-die extrusion molding. It is a polypropylene press-formed sheet obtained by further press-forming the obtained sheet.

Here, the syndiotactic polypropylene in the present invention is essential that the syndiotactic pentad fraction measured by ¹³ C-NMR is 0.7 or more, but the co-polymerization with other monomers In the case of coalescence, the syndiotactic pentad fraction needs to be at least 0.5 or more.

Examples of catalysts for producing these syndiotactic polypropylenes include, for example, JP-A-2-41303.
Japanese Patent Application Laid-Open No. 2-41305, Japanese Patent Application Laid-Open No. 2-27
4703, JP-A-2-274704, JP-A-3-179005, JP-A-3-179006, and JP-A-4-69394 having mutually asymmetrical ligands. Examples of the catalyst include a bridged transition metal compound and a co-catalyst, and even if the catalyst has a different structure, the syndiotactic pentad fraction measured by ¹³ C-NMR is 0.
Any polypropylene can be used as long as it can produce 7 or more polypropylene, and the polymerization method thereof can be a slurry polymerization method, a bulk polymerization method, or a gas phase polymerization method.

The syndiotactic polypropylene used in the present invention is a comonomer other than propylene, such as ethylene, 1-butene, 1-hexene, 1 as long as it does not impair the transparency of the press-formed sheet of the present invention.
A copolymer containing a small amount of olefins such as decene, 1-hexadecene, cyclopentene and norbornene, and diene such as hexadiene, octadiene, decadiene, dicyclopentadiene and 5-ethylidene-2-norbornene may be used. Such a copolymer can be obtained by copolymerizing propylene and a small amount of a comonomer in the presence of a known catalyst which gives the above-mentioned poly α-olefin having high syndiotacticity.

The molecular weight of the syndiotactic polypropylene thus obtained is 0.05 as a melt flow index (hereinafter abbreviated as MFI) at 230 ° C.
-100 g / 10 min, preferably 0.1-50 g /
10 min, more preferably 0.5 to 20 g / 10 min in consideration of molding processability of resin including press molding
Range.

Ethylene / α-used in the present invention
The olefin random copolymer elastomer is an elastomer having a copolymerization component of α-olefin having 3 or more carbon atoms of 15% by weight or more, and the press-formed sheet has flexibility of 300 kg / cm ² or less. Where α-
Examples of the olefin include butene-1, pentene-1, hexene-1, octene-1, 4-methylpentene-1 and the like.

Further, the present copolymer elastomer has the above-mentioned α-
It can be obtained by copolymerizing olefin and ethylene, but the catalyst system used must be a homogeneous catalyst, and examples thereof include vanadium-based and metallocene-based catalysts, but at least one aromatic Preferable examples include metallocene catalysts using a transition metal compound having a system ligand, particularly a complex of titanium, zirconium and hafnium. For example, a metallocene catalyst as described in US Pat. No. 5,278,272 can be used for polymerization, and the polymerization method can be carried out by a known method.

MF of the ethylene / α-olefin random copolymer elastomer thus obtained at 230 ° C.
I is 0.1 to 100 g / 10 min, preferably 0.
It is in the range of 5 to 60 g / 10 min.

In the present invention, a polypropylene resin composition comprising 5 to 30 parts by weight of syndiotactic polypropylene and 95 to 70 parts by weight of an ethylene / α-olefin random copolymer elastomer is used. Can be properly selected according to the purpose,
Preferably syndiotactic polypropylene is 10 to
25 parts by weight.

If the ratio of the ethylene / α-olefin random copolymer elastomer is less than 70 parts by weight, the flexural modulus is 700 kg / cm ² or more, and ASTM D8
It is not preferable because it lacks flexibility as a soft plastic as defined in 33, and when it exceeds 95 parts by weight, it has good transparency and flexibility, but it is released from the mold while the sheet is in close contact with the molding plate during press molding. Not only will the moldability be poor, but the sheets after molding will also block, which is undesirable.

The polypropylene-based resin composition of the present invention contains, if necessary, a heat stabilizer and a weather resistance stabilizer which are usually used for polypropylene-based resins, unless they significantly impair the transparency and flexibility of the press-formed sheet. Agent, ultraviolet absorber, radiation resistant agent, crystal nucleating agent, inorganic filler, lubricant,
Various additives such as plasticizers, organic peroxides, neutralizing agents, cross-linking agents, pigments and dyes can be added.

The polypropylene resin composition used in the present invention is prepared by mixing the syndiotactic polypropylene, the ethylene / α-olefin random copolymer elastomer and, if necessary, various additives with a mixer such as a Henschel mixer. It can be produced by melt-kneading and granulating using an extruder, Banbury mixer, pressure kneader, roll or the like.

As a method of press-molding, a method of press-molding granulated pellets as it is cannot obtain a sufficiently uniform molded product, and therefore calender molding or T molding is performed.
-It is necessary to prepare a raw sheet in advance by die extrusion and press-mold one or a plurality of stacked sheets. As the press molding machine, either a preheating plate and a cooling plate may be separate, or steam and cooling water may be alternately flowed through the pipes in the press plate to perform heating and cooling by one unit. Further, in the molding conditions, the heating temperature is not particularly limited as long as the resin can be plasticized, but considering that the temperature or cooling time of the cooling water is a method of slow cooling in press molding, the composition used in the present invention. Then, the transparency is good, but it is preferable in terms of productivity that the molten resin is cooled as quickly as possible.

Here, 23 of the polypropylene resin composition is used.
The MFI at 0 ° C. is preferably 0.5 to 20 g / 10 min in terms of moldability in press molding. A feature of the present invention is that the polypropylene resin composition is calendered or T-die extruded, and then press-formed to have flexibility equivalent to a soft plastic defined in ASTM D833 and transparency. This is where good sheets can be obtained.

[0023]

EXAMPLES The following examples are provided for illustrating the present invention further in detail, but the present invention is not limited thereto. The measuring method in the examples is as follows. (1) Melt flow index: ASTM D123
Compliant with 8. (2) Haze: According to ASTM D1003. (3) Flexural modulus: According to ASTM D790. (4) Releasability: The resistance at the time of peeling the sheet from the steel plate after press molding was evaluated as follows (⊚: easily peelable without resistance, ◯: with some resistance but with no problem, × : Resistance is large and difficult to peel off).

Example 1 Obtained by bulk polymerization of propylene in the presence of hydrogen using a catalyst consisting of diphenylmethylene (cyclopentadienyl) fluorenylzirconium dichloride and methylaluminoxane according to JP-A-2-274763. Syndiotactic homopolypropylene (2
MFI of 30 ° C. is 3.2 g / 10 min, peak temperature of crystallization temperature measured by differential scanning calorimetry is 74.6 ° C.,
Crystal melting point of 130 ° C., syndiotactic pentad fraction of 0.767, and 15 parts by weight of SPP), and an ethylene butene random copolymer elastomer obtained by a vanadium-based homogeneous catalyst (Toughmer A4085, 230)
MFI at ℃ = 6.7 kg / 10 min, Mitsui Petrochemical Co., Ltd.) 85 parts by weight, as an antioxidant Irgaphos 168 (Ciba Geigy) 0.10 parts by weight, and Irganox 1010 (Ciba Geigy) Company) 0.0
5 parts by weight, calcium stearate as a neutralizing agent 0.0
After adding 2 parts by weight and mixing with a Henschel mixer,
Granulation was performed with an extruder at a cylinder temperature of 210 ° C.

Next, the pellets were extruded by a T-die extrusion film forming machine to obtain an extruded sheet having a thickness of 0.5 mm.
4 sheets of this sheet are piled up, thickness 2mm, size 150 × 1
Put it in a mold for making a 50 mm sheet, sandwich it between steel plates, then sandwich it between heating plates heated to a temperature of 250 ° C, preheat for 10 minutes, and then press the plate with a total weight of 60 kg at 20 ° C enough to cool it as quickly as possible. A press sheet was obtained by press-cooling for 10 minutes at a pressure of 200 kg / cm ² with a press molding machine through which a large amount of cooling water was passed. This sheet had a haze of 39% and a flexural modulus of 550 kg / cm ² , and was excellent in transparency and flexibility. The results are shown in Table 1.
Shown in

Example 2 The elastomer to be blended was an ethylene butene random copolymer elastomer polymerized by a metallocene catalyst (Exact 4041, MFI at 230 ° C. = 5.5 g /
A sheet was obtained in the same manner as in Example 1 except that 10 min, manufactured by Exxon) was used. The haze of this sheet is 17
%, The bending elastic modulus was 530 kg / cm ² , and the transparency was good and the flexibility was also excellent. The results are shown in Table 1.

Example 3 The elastomer to be blended was an ethylene octene random copolymer elastomer polymerized by a metallocene catalyst (Engage 8200, MFI at 230 ° C. = 9.8).
g / 10 min, manufactured by Dow) was used to obtain a sheet in the same manner as in Example 1. The haze of this sheet is 20
%, The flexural modulus was 460 kg / cm ² , and the transparency was good and the flexibility was also excellent. The results are shown in Table 1.

Example 4 A sheet was obtained in the same manner as in Example 2 except that the SPP ratio was 10 parts by weight. The sheet haze was 14%, the flexural modulus was 370 kg / cm ² , and the transparency was good and the flexibility was also excellent. The results are shown in Table 1.

Example 5 A sheet was obtained in the same manner as in Example 2 except that the proportion of SPP was 25 parts by weight. The sheet haze was 34%, the flexural modulus was 670 kg / cm ² , and the transparency was good and the flexibility was also excellent. The results are shown in Table 1.

Example 6 As a method for obtaining a raw material for press molding, a mixing roll consisting of two rolls and an inverted L-type calender forming machine consisting of four rolls were used instead of T-die extrusion film forming, and a roll temperature of 150 was used. A sheet having a thickness of 0.5 mm was obtained in the same manner as in Example 2, except that the sheet was calendered at ℃. This sheet had a haze of 18% and a flexural modulus of 550 kg / cm ² , and was excellent in transparency and flexibility. The results are shown in Table 1.
Shown in

Comparative Example 1 Instead of SPP and elastomer, isotactic polypropylene (JHH-G, 230 ° C. MFI = 8).
A sheet was obtained in the same manner as in Example 1 except that 100 parts by weight of g / 10 min, manufactured by Mitsui Toatsu Chemicals, Inc.) was used. This sheet has a haze of 90% and a flexural modulus of 18,000 kg /
cm ² , the transparency was very poor, and there was no flexibility at all. The results are shown in Table 1.

Comparative Example 2 A sheet was obtained in the same manner as in Example 1 except that 100 parts by weight of SPP was used without using an elastomer.
This sheet has a haze of 24% and a flexural modulus of 6200k.
It was g / cm ² , and the transparency was good, but the flexibility was insufficient. In addition, since the solidification rate of the resin during pelletization is slow, strand cutting is difficult to occur, which causes a problem in productivity. The results are shown in Table 1.

Comparative Example 3 A sheet was obtained in the same manner as in Example 2 except that 50 g of granulated pellets were directly sandwiched in a press molding machine and press-molded without forming a raw sheet by T-die extrusion molding. . This sheet has a haze of 48% and a flexural modulus of 510 kg / c.
It was m ² , and the transparency was poor, and the sheet was uneven. The results are shown in Table 1.

Comparative Example 4 A sheet was obtained in the same manner as in Example 2 except that the proportion of SPP was 35 parts by weight. The sheet haze was 44% and the flexural modulus was 960 kg / cm ² , indicating insufficient flexibility. The results are shown in Table 1.

Comparative Example 5 A sheet was obtained in the same manner as in Example 2 except that 100 parts by weight of elastomer was used without using SPP. This sheet has a haze of 10% and a flexural modulus of 140 kg / c.
Although it was m ² , the transparency was good and the flexibility was excellent, but the sheet adhered to the molding plate during press molding, resulting in poor release. The results are shown in Table 1.

[0036]

[Table 1]

[0037]

INDUSTRIAL APPLICABILITY The polypropylene-based resin press-formed sheet of the present invention is suitable for a soft sheet because it has good transparency and excellent flexibility as compared with a normal isotactic polypropylene press-formed sheet. For example, a desk mat or the like. Can be expected to be used.

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Claims (3)

[Claims] 1. Syndiotactic polypropylene 5 to 3
A sheet obtained by calender molding or T-die extrusion molding of a polypropylene resin composition consisting of 0 parts by weight and 95 to 70 parts by weight of an ethylene / α-olefin random copolymer elastomer is obtained by further press molding. Polypropylene press-formed sheet. 2. The polypropylene press-formed sheet according to claim 1, wherein the ethylene / α-olefin random copolymer elastomer is obtained by polymerizing ethylene and α-olefin using a homogeneous catalyst. 3. The polypropylene press-formed sheet according to claim 1, wherein the homogeneous catalyst is a metallocene catalyst.