JP3221046B2 - Polycarbonate hollow molded product with excellent steam resistance - Google Patents

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 of polycarbonate, and more particularly, to a polycarbonate molded article which is excellent in heat resistance, steam resistance and solvent resistance, and is preferably used in the food and medical fields. It is intended to provide a hollow molded product.

[0002]

2. Description of the Related Art Conventionally, hollow molded articles molded from a thermoplastic resin have been used in a variety of liquid-filled containers for beverages, cosmetics, detergents, and the like. However, in recent years, from the viewpoint of the global environment, resource conservation and reduction of waste have been called for, and plastic products have been reviewed, and these hollow molded products are no exception. As a result, there has been a demand for a returnable hollow molded product that can be refilled through conventional collection, cleaning and disinfection of containers from disposable.

[0003] Polycarbonate hollow molded articles have hitherto been used for applications that take advantage of their transparency, heat resistance and fragrance retention. However, polycarbonate has a drawback that the drawdown at the time of blow molding is large, the uneven thickness of the molded product is large, and it is difficult to mold.
Its use was in a situation where only small hollow molded articles such as baby bottles and eye drops containers, which were relatively easy to mold, could be formed.

However, in recent years, blow polycarbonates having improved drawdown resistance by introducing a branched structure have been developed. Although there is still a problem in moldability, a relatively large hollow mold utilizing the transparency of polycarbonate has been developed. Goods are becoming available. In addition, there has been an increasing movement to expand applications from the social environment described above to relatively large hollow molded articles such as returnable containers for drinking water and milk.

[0005]

However, a general polycarbonate hollow molded article is susceptible to hydrolysis because of its chemical structure, and when exposed to steam or high-temperature water, the molecular weight and the transparency are reduced. Has problems. Furthermore, hollow molded products made of polycarbonate for blowing with a branched structure have a lower hydrolysis resistance than linear polycarbonate, so they are used as returnable hollow molded products with steam cleaning. There was a problem that the life was short.

Accordingly, a polycarbonate hollow molded article which can sufficiently withstand repeated washing with steam, particularly a relatively large polycarbonate hollow molded article, has not been obtained so far, and its appearance is awaited. As a method of improving the hydrolysis resistance of polycarbonate, it is generally performed to reduce the amount of a phosphorus-based stabilizer used as a heat-resistant stabilizer or to use a phosphorus-based stabilizer excellent in hot water resistance. . However, even with this improvement, the improvement of the steam resistance was insufficient, and especially the improvement of the hollow molded article using the branched polycarbonate was insufficient.

We have proposed a hollow molded article made of polycarbonate which can be repeatedly sterilized with steam, especially a relatively large hollow molded article of 500 ml or more, for example, a medical container such as a returnable container for drinking water or milk or a suction bottle for surgery. As a result of repeated studies to obtain a container, the weight average molecular weight (Mw) 4
Even if a hollow molded article made of a high-molecular-weight polycarbonate which is substantially free of chlorine atoms and is substantially linear and has a relatively large size is 3,000 to 300,000, the thickness of the product is small and the thickness of the molded article is practical and surprising. It was found that the steam resistance was extremely excellent, and the present invention was reached.

[0008]

That is, the present invention relates to a hollow molded article obtained by blow molding polycarbonate, wherein the polycarbonate has a weight average molecular weight (M) before molding.
The present invention provides a hollow polycarbonate molded article having excellent steam resistance, wherein w) is 40,000 to 300,000 and is a substantially linear high molecular weight polycarbonate.

The hollow molded article of the present invention having excellent steam resistance can be obtained by blow molding a specific polycarbonate. The polycarbonate used for obtaining the hollow molded article of the present invention is a substantially linear polycarbonate having a main chain composed of a repeating unit represented by the formula (1).

[0010]

Embedded image In the formula, Ar is a divalent aromatic residue, and examples thereof include phenylene, naphthylene, biphenylene, and pyridylene, and those represented by the formula (2).

[0011]

## STR2 ## -Ar ¹ -Y-Ar ² - Equation (2) wherein, Ar ¹ and Ar ² are each an arylene group, or for example, phenylene, naphthylene, biphenylene, a group such as pyridylene, Y Is an alkylene group or a substituted alkylene group represented by the following formula 1. ]

[0012]

Embedded image Further, a divalent aromatic residue represented by the formula (3) may be contained as a copolymer component.

[0013]

Embedded image —Ar ¹ —Z—Ar ² — Formula (3) wherein Ar ¹ and Ar ² are the same as described above, and Z is a mere bond or —O—, —CO—, or —S— , -SO _2- ,
-CO _2- , -CON (R ¹ ) (R ² )-, (R ¹ , R
² is the same as described above). Examples of these divalent aromatic residues include, for example,
And the like represented by Chemical Formula 7.

[0014]

Embedded image

[0015]

Embedded image

[0016]

Embedded image Wherein R ⁵ and R ⁶ are each hydrogen, halogen,
C ₁ -C ₁₀ alkyl group, C ₁ -C ₁₀ alkoxy group, C ₅
~ C ₁₀ cycloalkyl group or phenyl group, m and n are integers of 1 to 4, and when m is 2 to 4, each R ⁵ may be the same or different; Is 2
In the case of to 4, each R ⁶ may be the same or different. Among them, a compound represented by the following formula is a preferable example.

[0017]

Embedded image In particular, 85 repeating units each having the above formula 8 as Ar
Those containing at least mol% are preferred.

In the present invention, “substantially linear” means that a trifunctional or more branched structure is not intentionally introduced. Therefore, a small amount of a branched structure due to a small amount of impurities when introducing the repeating unit may be contained. For example, in commercially available 2,2-bis (4-hydroxyphenyl) propane (bisphenol A),
Contains up to about 0.01 mol% of trifunctional compounds.
However, such a content does not impair the features of the present invention. When a trifunctional or more branched structure is intentionally introduced, the steam resistance is undesirably reduced.

Although the molecular structure of the terminal of the polymer is not particularly limited, one or more terminal groups selected from a hydroxyl group, an aryl carbonate group and an alkyl carbonate group can be bonded. Aryl carbonate group terminal is the following formula

[0020]

Embedded image [In the formula, Ar ³ is a monovalent aromatic residue. The aromatic ring may be substituted. ], As a specific example, for example,

[0021]

Embedded image And the like. The terminal of the alkyl carbonate group is represented by the following formula

[0022]

Embedded image [Wherein, R ⁷ is a linear or branched alkyl group having 1 to 20 carbon atoms], and specific examples include, for example,

[0023]

Embedded image And the like. Among these, a phenyl carbonate group, a pt-butylphenyl carbonate group, a p-cumylphenyl carbonate group, and the like are preferably used. The hydroxyl group terminal is preferably as small as possible to reduce heat resistance and hot water resistance.

The weight average molecular weight (Mw) of the polycarbonate constituting the hollow molded article of the present invention is from 40,000 to 3
It is in the range of 00,000. 40,0 weight average molecular weight
If it is smaller than 00, the steam resistance is not sufficiently improved, and the drawdown is large. If the weight average molecular weight is more than 300,000, the melt viscosity becomes too high and extrusion cannot be performed, which is not preferable. Preferably, it is in the range of 40,000 to 100,000, and more preferably in the range of 40,000 to 80,000. In particular, a weight average molecular weight in the range of 45,000 to 65,000 is preferable from the viewpoint of balance between steam resistance, drawdown resistance (uneven thickness of a hollow product) and extrudability.

The measurement of the weight average molecular weight (Mw) in the present invention is performed by using GPC, and the measurement conditions are as follows. Using a tetrahydrofuran solvent and a polystyrene gel, it was determined from a constitutive curve of a standard monodisperse polystyrene using a reduced molecular weight calibration curve according to the following equation.

[0026]

[Number 1] ^{_{M PC = 0.3591M PS 1.0388 (M}} PC molecular weight of the polycarbonate, M _PS molecular weight of polystyrene) The polycarbonate constituting the hollow molded article of the present invention is not particularly limited, substantially It is preferable that a chlorine atom is not contained in view of steam resistance and stability during blow molding. The chlorine atom is a chlorine ion measured by a potentiometric titration method using an AgNO ₃ solution and a chlorine atom measured by a combustion method.
0.0005% by weight or less and 0.001% by weight or less of polycarbonate are preferably used.

These polycarbonates can be produced by a known method. Specific examples include known methods for reacting an aromatic dihydroxy compound with a carbonate precursor, for example, an interfacial polymerization method in which an aromatic dihydroxy compound is reacted with phosgene (phosgene method), and an ester in which an aromatic dihydroxy compound is reacted with diphenyl carbonate. It can be produced by a method such as an exchange method (melting method) or a method of solid-phase polymerization of a crystallized carbonate prepolymer. Above all, a polycarbonate obtained by a solid phase polymerization method is preferable because it can be easily obtained without substantially containing a chlorine atom, and is excellent in steam resistance and high-temperature blow moldability.

The hollow molded article of the present invention can be obtained by blow molding the above-mentioned specific polycarbonate. The blow molding method and molding conditions are not particularly limited, and molding is performed by a known method. However, since the weight average molecular weight is higher than that of ordinary polycarbonate, the molding temperature needs to be set high. In particular, in order to obtain a polycarbonate hollow molded article with less uneven thickness, it is preferable to perform blow molding in a temperature range where the melt viscosity of the parison is 10 ⁶ poise or more. It is also preferable to slightly increase only the parison surface temperature at the die lip to improve the surface appearance.

Hereinafter, an embodiment will be described in detail. (Measurement of MI) Measurement temperature 2 according to ASTM D1238.
The test was performed at 80 ° C. with a load of 2.16 kg. (Evaluation of Drawdown) At the time of blow molding, the parison that came out was dropped freely and visually evaluated. (Measurement of uneven thickness) 20 mm and 140 m from the top of the molded product
The wall thickness of the portion m was measured and calculated by the following equation.

[0030]

(Equation 2) (Steam resistance test) The molded article was exposed to steam at 120 ° C using a steam sterilizer. 200 hours and 400
After a lapse of time, the light transmittance and the weight average molecular weight were measured. The light transmittance was evaluated at a wavelength of 520 nm by cutting out a molded product after the steam resistance test.

[0031]

【Example】

Examples 1, 2, 3 A substantially linear high molecular weight polycarbonate (weight average molecular weight = 45) prepared from diphenyl carbonate and 2,2-bis (-hydroxyphenyl) propane according to the method of JP-A-3-68627. 000,56,00
0, and 75,000) by a blow molding machine with a thickness of 1.5 mm, an outer shape of 90 × 150 × 220 mm, and an inner capacity of 2
A liter square can was molded at a molding temperature of 260 ° C and a mold temperature of 80 ° C. Table 1 shows the drawdown at the time of molding, the results of the measurement of uneven thickness of the molded product, and the results of the steam exposure test.

Comparative Examples 1 and 2 The weight average molecular weight produced by the phosgene method was 28,000.
A substantially linear polycarbonate and also 36,
2,000 branched polycarbonates were molded in the same manner as in Example 1 to obtain 2-liter square cans. However, 28,0
For polycarbonate No. 00, the drawdown was severe, and no molded product was obtained. Table 1 shows the evaluation results.

[0033]

As shown in the examples, the hollow molded article of the present invention has little uneven thickness and is extremely excellent in steam resistance.

[0034]

[Table 1]

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-331276 (JP, A) JP-A-3-68627 (JP, A) JP-A-4-253766 (JP, A) 279659 (JP, A) JP-A-5-70659 (JP, A) JP-A-4-342760 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 49/00-49 / 80 C08G 64/04-64/42 C08L 69/00

Claims (1)

(57) [Claims] 1. A hollow molded article obtained by blow molding polycarbonate, wherein the polycarbonate has a weight average molecular weight (Mw) of 40,000 to 300,00 before molding.
0. A hollow polycarbonate molded article having excellent steam resistance, characterized in that the molded article is a substantially linear high molecular weight polycarbonate.