JPS6099108A - Preparation of molded article of polypropylene - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a polypropylene molded article that prevents the occurrence of uneven gloss.

Polypropylene is commonly used as fiber and film.

Although it is widely used as molded products such as sheets and structures, it has the problem that uneven gloss occurs on the surface of the injection molded product depending on the molding conditions, which significantly reduces its commercial value. A technique that has been attracting particular attention recently is a method in which a polymer with a large molecular weight is produced and then decomposed by the action of radicals to reduce the molecular weight to obtain polypropylene with a desired molecular weight. When injection molded products are manufactured using the obtained polypropylene (hereinafter also referred to as decomposed PP), uneven gloss is noticeable.

The present inventors have conducted intensive research on preventing uneven gloss when producing injection molded polypropylene products. As a result, it was found that the molecular weight distribution of polypropylene has a significant effect on the uneven gloss on the surface of injection molded products of the polypropylene. That is, as polypropylene decomposes, its molecular weight decreases and its molecular weight distribution narrows, and as the molecular weight distribution narrows, the above-mentioned problems become more pronounced. Based on the knowledge of the present invention, weight average molecular weight (Mw) and number average molecular weight (Mn) representing molecular weight distribution
Production of a polypropylene molded product that almost completely prevents the occurrence of gloss unevenness on the surface of the resulting polypropylene injection molded product by injection molding using BoIJ7'ropylene having a ratio of 6 or more (Mw1Mn ratio) provide a method.

That is, the present invention is a method for producing a polypropylene molded article, characterized by using polypropylene having a U, /Un ratio of 6 or more.

In the present invention, polypropylene is a general term for propylene homopolymers and copolymers with propylene and other α-olefins, such as ethylene. Furthermore, the term "molded product" is a general term that includes structures generally obtained by injection molding, as well as plate-like bodies, sheet-like bodies, and the like.

In the present invention, it is extremely important to use polypropylene with a M W /M n ratio of 6 or more, preferably 7 or more in order to obtain a molded product with no uneven gloss on the surface. That is, in the present invention, when the molecular weight distribution expressed by the MW/Mn ratio becomes narrower than the above-mentioned certain range due to manufacturing conditions or decomposition treatment, uneven gloss on the surface of the injection molded product obtained becomes significant. It is based on new knowledge. Therefore, a molded article obtained by incorporating polypropylene having an M,/Mn ratio smaller than the above range has a significant uneven gloss on its surface, making it impossible to achieve the object of the present invention. In addition, in terms of strength, such as the bending modulus of the molded product, the polypropylene weighs only 7g.

The ratio is less than 10, preferably 8 or less, or melt flow index (hereinafter also referred to as MI) h's 6 or more
・゛Things/I'-IIf 0 used.

Mw/M in the above range. Polypropylene having a Mw/Mn ratio that has been polymerized or adjusted to have an Mw/Mn ratio within the range by a known means of broadening the molecular weight distribution can be used without any particular restriction. For example, JP-A-5 (S-2307)
No., Japanese Patent Application Publication No. 5 <S-157407, Japanese Patent Application Publication No. 54-8
A method of polymerizing propylene so that the M W / M n ratio falls within the above range using a special catalyst that widens the molecular weight distribution as shown in No. 6586 etc. (catalytic method), polymerization conditions, e.g. molecular weight during polymerization By changing the amount of the modifier stepwise, the molecular weight distribution of the polypropylene produced can be adjusted to the above w/M. A method of adjusting the ratio (microblend method) is to mix polypropylenes with different molecular weights and adjust the molecular weight distribution to the above Mw/M. Examples include those obtained by adjusting the ratio (tri-blend method) alone or in combination. In particular, those obtained by the catalytic method and the microblend method are suitable in the present invention.

In the present invention, when Te decomposition pp is used as polypropylene, the MW/round ratio tends to decrease significantly due to decomposition. The entrainment and decomposition may be carried out using polypropylene having a relatively high K Mw/Mn ratio as a raw material. Generally, the MW/Mn ratio is 10 or more, preferably 10 to 50.
, More preferably, 15 to 3o polypropylene is used as a raw material, and this is decomposed to produce decomposed PP having the above Mw/Mn ratio.
It is preferable to do so. Of course, the decomposition pp ke, M +, y/
M (Even if raw material polypropylene with a ratio of less than 10 is decomposed, if the decomposition rate is increased in order to increase the tI of the decomposed PP and improve processability, it will take longer to decompose to the desired molecular weight. The Mw/MH ratio may exceed the lower limit, making it difficult to reduce the molecular weight sufficiently.The raw material polypropylene having the high M,/Mn ratio can be obtained by the known means described above. In addition, the decomposition of the raw material polypropylene can be carried out by any known method, although there are no particular restrictions.In general, a method in which polypropylene is heat-treated in the presence of a radical generator is suitable.

As the radical generator, an organic peroxide is preferably used. Examples of typical organic peroxides include ketone peroxides such as methyl ethyl ketone peroxide and methyl imbutyl ketone peroxide; diacyl peroxides such as im butyl peroxide and acetyl peroxide; diimpropylbenzene hydroper. Oxide, other hydroperoxide; 2,5
-dimethyl 2,5-di(t-butylperoxy)hexane.

1.3-bis-(1-butylperoxyimprovil)
Dialkyl peroxide such as benzene: 1,1-di-
t-Butyl peroxy-cyclohexane, other peroxyketals: t-butyl peroxy acetate, t
Examples include alkyl peresters such as -butylperoxybenzoate; t-butylperoxyinpropyl carbonate and other percarbonates. The amount of the organic peroxide to be used varies depending on the set value of the molecular weight of polypropylene after decomposition, etc., and cannot be determined unconditionally, but it is 0.0 D 1 to 1.0% by weight, preferably 0.01 to 1.0% by weight, based on the polypropylene. L5% by weight is common.

Further, in the above method, the method for mixing polypropylene and the radical generator is not particularly limited as long as the radical generator is present when the polypropylene is heat treated. For example, there is a method of mechanical mixing using a mixer such as a Plengy, a method of dissolving a radical generator in a suitable solvent, adhering it to polypropylene, and mixing by drying the solvent. Further, the heat treatment temperature is a temperature higher than the melting temperature of BoI77'ropyrene and higher than the decomposition temperature of the radical generator.

However, if the heat treatment temperature is too high, thermal deterioration of polypropylene will occur. Generally, the heat treatment temperature is 170-3
00C,% is preferably set within the range of 18D to 250C.

As can be understood from the above explanation, the injection molded product obtained by the method of the present invention has almost no uneven gloss on the surface.
In particular, it is suitably employed because it exhibits excellent effects in the production of molded products using decomposed PP, where occurrence of surface gloss unevenness is a major problem in injection molding.

In the method of the present invention, when obtaining a molded article by injection molding,
Although it is particularly effective, it can also be applied to the production of molded products such as sheets and films by other molding methods, such as extrusion molding, without any particular problem.

EXAMPLES Hereinafter, examples will be shown to specifically explain the present invention, but the present invention is not limited to these examples.

The various properties shown in the following Examples and Comparative Examples were measured by the following methods.

(1) Melt index (also written as MI) AS
TM, D-1238 (2) Ethylene content The ethylene content in the block copolymer was determined by infrared absorption spectrometry.

(3) Molecular weight distribution Mw/h.

The measuring device used was C) PC150C manufactured by Waters.
The solvent was 0-dichlorobenzene, and the measurement temperature was 135°C.

(4) Visually observe the injection molded test piece for measuring uneven gloss flexural modulus. If no uneven gloss is observed, mark ◎, if very slight unevenness is observed, mark ○, if slightly observed, mark △ , and other items were rated as ×.

Generally speaking, uneven gloss tends to appear in concentric circles than in Kate. The period changes depending on injection molding conditions.

(5) Flexural modulus The test piece is Nikko Ankelberg V22A. -Made using a 120-type injection molding machine, Measured by A'EITMD-790.

(6) Izotsu impact strength The test piece was prepared in the same way as the bending test piece. Measured by ASTM D-256.

Example 1 In a 600 t agitated polymerization tank purged with propylene gas, 20
twice the molar amount of diethylaluminum monochloride (AtE
t2C1) and 0.02 times the mole of diethylene glycol dimethyl ether (also described as Dig4yme), then 200% liquid propylene and hydrogen gas as a molecular regulator were introduced and the temperature was raised to 65°C, followed by TLCA4. (Manufactured by Marubeni Nlevet) 3.
Polymerization was started by adding 49. During the polymerization, hydrogen gas was supplied and the gas phase concentration was controlled using gas chromatography to keep it constant. First, the gas phase hydrogen concentration was set to 13.6 mol% so that the MI of the polymer to be polymerized was 500.
The polymerization was continued for 1 hour and 20 minutes. Then, only unreacted propylene and hydrogen were purged from the top of the polymerization tank.

Subsequently, 150 tons of propylene and 15 times the mole of AtFit2Ct were added again to the polymerization tank where the polymerization polymer remained, and hydrogen gas was introduced. Then, the temperature was raised to 65'C and polymerization was restarted.

During the polymerization, hydrogen gas is supplied, and the gas phase hydrogen concentration is adjusted to 0.6 so that the MI of the polymer produced in the polymerization step is 0.01.
Polymerization was continued for 3 hours at a concentration of 5 mol %. After the polymerization is completed, the polymer slurry is discharged from the bottom discharge valve of the polymerization tank into a flash tank, unreacted propylene is purged to stop the polymerization, and then 200 ml of heptane and 40 ml of methanol are added.
The slurry was made into a slurry and stirred at 60°C for 1 hour to decompose the catalyst. Subsequently, 100 ml of water was injected, the catalyst decomposition product was extracted into the aqueous phase, and the aqueous phase was separated and removed. The hebutane slurry of the polymer was separated into solid and liquid using a centrifuge, and the solid was sent to a dryer and dried for 6 hours to obtain a white granular crystalline polymer. On the other hand, a portion of the filtrate was collected and after heptane was removed, AP
P was recovered. The MI of the polymer is 1.8. The APP by-product rate was 3.4%.

The organic peroxide 1,3-bis(t-butylperoxyimprobyl)benzene (also referred to as BPB) was added to the white granular polypropylene thus obtained in the proportions shown in Table 1, and an antioxidant, jealousy was added. A stabilizer and a lubricant were added and mixed using a Henschel mixer. Next, Nakatani Machinery VSK
The polymer was decomposed and extruded using a 40 m + φ extruder equipped with a vent while controlling the resin temperature at the exit of the die to #z230'c, and extruded to obtain a pellet-like polymer. The Ml, molecular weight distribution 9/circle, gloss unevenness, and flexural modulus of the polymer were evaluated. The results are shown in Table-1.

Table-1 ] ] ] ] ] *Mu1 is untreated Example 2 Using the same equipment as in Example 1, 20 times the molar amount of AtEt2C
L and 0.02 times the mole of Diglime were added, then 200% of liquid propylene and hydrogen gas were introduced, and the temperature was raised to 65° C., followed by the addition of TiCLS-3,5f to initiate polymerization. Hydrogen gas was supplied during the polymerization, and the hydrogen gas phase concentration was controlled by gas chromatography so that the MI car of the produced polymer was 1.7. After 3 hours of polymerization, the polymer slurry was discharged into a flash tank from the bottom drain valve of the polymerization tank, and the unreacted propylene was removed to stop the polymerization. The subsequent treatment was carried out in the same manner as in Example 1, and white granular (1) #q', I
Akira? +i weight itself was obtained. The MI of the polymer is 1.7. AP
The by-product rate of P is 0.8%.

Subsequently, the same organic peroxide as in Example 1 was added to the polymer in Table 2.
Mix as shown in , and add antioxidant, heat stabilizer,
A lubricant was added and mixed in a Henschel mixer. Thereafter, the same procedure as in Example 1 was carried out to obtain a pellet. The physical properties of the polymer were measured in the same manner as in Example 1, and the results are shown in Table 2.

Table 2 Example 3 Using the white granular polypropylene polymerized in Example 1, 2,5-dimethyl-2,5-di(t-butylperoxy) shown in Table 3 was used instead of the organic peroxide BPB. ) hexane (also written as MBH), 1,1-di-t-butylperoxy-3,3,541J methylcyclohexane (B
A pellet was obtained in the same manner as in Example 1 except that t-butylperoxyinpropyl carbonate (also referred to as MC) and t-butylperoxyinpropyl carbonate (also referred to as BPC) were used. The physical properties of the polymer were measured in the same manner as in Example 1, and the results are shown in Table 6. Table 3 Comparative Example 1 Example except that the white granular polypropylene polymerized in Example 2 was used. A pellet was obtained by disassembly treatment in the same manner as in 3. The physical properties of the polymer were measured in the same manner as in Example 1, and the results are shown in Table 4.

Table 4 Example 4 (A) Synthesis of Aluminum Ethoxy Into a 2 t flask purged with nitrogen, 604 ml of a heptane solution containing 20 wt% of p-tEt and 610 mL of a heptane solution containing 20 wt% of AtEt2cL were charged. Then add ethanol to 1. A heptane solution 302- containing Owt% was gradually added dropwise and mixed at room temperature. After the dropwise addition was completed, the temperature was raised to 70°C and reaction was carried out for 1 hour to synthesize aluminum ethoxy.

(B) Perform polymerization of polypropylene Using a volumetric apparatus, add 750 d of aluminum ethoxy synthesized in (A) and 0.15 d to the aluminum □.
20 times the mole of p-ethyl anisate and liquid propylene
While adding OL and hydrogen as a molecular weight regulator, 65
℃, and TiCA3 was heated to 7. Polymerization was started by adding Of. During the polymerization, hydrogen gas was supplied and the hydrogen gas phase concentration was controlled by gas chromatography so that the MI of the produced polymer was 1.7. After 6 hours of polymerization,
The polymer slurry was discharged into a flash tank from the bottom discharge valve of the polymerization tank, and unreacted propylene was purged to stop the polymerization. The subsequent treatments were carried out in the same manner as in Example 1.

Incidentally, the MI of the obtained polymer was 1.9. The by-product rate of APP was 1.4%.

BPB was added to the thus obtained white granules of polypropylene in the proportions shown in Table 5, and the procedure was repeated in the same manner as in Example 1 to obtain pellets.

The physical properties of the polymer were measured in the same manner as in Example 1, and the results are shown in Table 5.

Table 5 Example 5 Polymerization of block copolymer Using the same catalyst system as in Example 1, MI of the polymer produced
Polymerization was carried out in the same manner as in Example 1, except that the polymerization time was set to 2.5 and the polymerization time was set to 2 hours.

The slurry of the produced propylene homopolymer was discharged into a flash tank, and after purging unreacted propylene, the slurry was transferred to the polymer slurry tank, and 150 tons of heptane was added thereto to form a slurry. Subsequently, the polymer slurry was
Transfer to a polymerization tank set at ℃ and add ethylene gas,
Propylene gas and hydrogen gas as a molecular weight regulator were supplied. The supply of ethylene gas and propylene gas was controlled by gas chromatography so that the molar ratio of ethylene/propylene in the gas phase region was 1/4, and the supply of hydrogen gas was controlled to be 20 mol% in the gas phase region. went. After carrying out the polymerization reaction for 2 hours under these conditions, the produced block copolymer was discharged into a flash tank to purge unreacted propylene, and then methanol 401 was injected to
C. for 1 hour to decompose the catalyst.

A white granular crystalline polymer was obtained by blowing in the same manner as in Example 1. The MI of the polymer is 1.6. The ethylene content was 4.2% by weight.

Organic peroxide BP is added to the block copolymer obtained by smelting.
B was mixed in the proportions shown in Table 6 using a Henschel mixer with the addition of an antioxidant, a heat stabilizer, and a lubricant. Next, Nakatani Machine v S K 40 40 gourd φ with vent
The resin was decomposed in an extrusion manner while controlling the resin temperature at the exit of the die to 230°C, and extruded to obtain a pellet-shaped polymer. The physical properties of the polymer were measured and shown in Table 6.

Table-6

Claims (3)

[Claims] (1) A method for producing a polypropylene molded article, characterized by using polypropylene having a ratio of weight average molecular weight (Mw) to number average molecular weight (terminal) (yrw/un ratio) of 6 or more. (2) The method according to claim (1), wherein the polypropylene is polypropylene whose molecular weight has been reduced by decomposition. (3) Mw/M of polypropylene before decomposition. The method according to claim (2), wherein the ratio is 10 or more.