JPH0310663B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a modified propylene that maintains the excellent impact resistance and other mechanical properties originally possessed by propylene-ethylene block copolymers, and has improved optical properties such as gloss and transparency, and impact whitening resistance. - A method for producing an ethylene block copolymer composition. Propylene-ethylene block copolymers (hereinafter sometimes abbreviated as P/E block copolymers) have excellent mechanical properties, especially impact resistance, as well as some excellent optical properties such as gloss and transparency. Because of this, its use as a molding material for various molded products is expanding. However, P/
A so-called impact whitening phenomenon occurs in molded products of E-block copolymer, in which the surface becomes cloudy due to impact, which significantly reduces the commercial value of the product, especially in products where the appearance of the molded product is important. Conventionally, a P/E block copolymer composition in which a P/E block copolymer is mixed with high density polyethylene has been proposed as a means for improving the impact whitening resistance of the P/E block copolymer. However, the molded products of the above compositions do not have sufficient impact whitening resistance. In addition, in order to improve impact whitening resistance, it is necessary to increase the mixing ratio of high-density polyethylene, and as a result, various properties originally possessed by P/E block copolymers, such as mechanical properties and optical properties, deteriorate. This creates the problem of The present inventors have already proposed a method for avoiding the above-mentioned problems and improving the impact whitening resistance of P/E block copolymers by mixing P/E block copolymers and high-density polyethylene and then decomposing them with an organic peroxide. proposed a method. Subsequently, as a result of further studies on the above method, it was found that after mixing low density polyethylene as a third component with the P/E block copolymer and high density polyethylene, the modified structure obtained by the above method was decomposed with an organic peroxide. It has been found that the transparency of the P/E block copolymer composition is significantly improved without impairing other properties such as impact whitening resistance, and the present invention has been completed. That is, the present invention provides a method for producing a modified propylene-ethylene block copolymer composition, which comprises heat-treating a mixture of a propylene-ethylene block copolymer, low-density polyethylene and high-density polyethylene in the presence of an organic peroxide. be. In the present invention, it is extremely important that the mixture of P/E block copolymer, low density polyethylene and high density polyethylene be heat treated in the presence of an organic peroxide. That is,
Even if P/E block copolymer, low-density polyethylene, and high-density polyethylene are heat-treated in the presence of an organic peroxide and then mixed together, the impact whitening resistance is not sufficiently improved, and the desired effect of the present invention is not achieved. barely able to achieve their goals. The method of mixing the P/E block copolymer, low density polyethylene and high density polyethylene is not particularly limited. For example, a method of mechanically mixing both in granular or powder form, or a method of polymerizing a P/E block copolymer described later and then polymerizing high-density polyethylene; A method of mechanically mixing polyethylene is preferred. In the above-mentioned mixing for polymerization, a new catalyst can be supplied as needed during the polymerization of high-density polyethylene. Also, ethylene monomer is 10
It may contain different monomers such as propylene and butene-1 within a range of up to % by weight. In the present invention, the organic peroxide is not particularly limited as long as it is present when the mixture of P/E block copolymer, low density polyethylene and high density polyethylene is heat treated. In general, the P/E block copolymer is premixed with low density polyethylene or high density polyethylene, the P/E block copolymer, low density polyethylene and high density polyethylene are simultaneously mixed at the time of mixing, and the P/E block copolymer is mixed with low density polyethylene or high density polyethylene at the same time. ,
An appropriate embodiment can be selected from among the embodiments in which low density polyethylene and high density polyethylene are mixed after mixing. As for the mixing method of the organic peroxide, any known mixing method may be used without particular limitation. For example, more uniform mixing can be achieved by dissolving the organic peroxide in a suitable solvent and depositing it on the P/E block copolymer, low density polyethylene and/or high density polyethylene and drying the solvent. be. The heat treatment temperature for the mixture of the P/E block copolymer, low density polyethylene and high density polyethylene is a temperature higher than the melting temperature of the mixture and higher than the decomposition temperature of the organic peroxide. However, if the heat treatment temperature is too high, it will cause thermal deterioration of the P/E block copolymer, low density polyethylene, or high density polyethylene, so generally the heat treatment temperature is 180°C.
It is preferable to perform the heat treatment in the range of ~300°C. In the present invention, P/E block copolymers obtained by known production methods can be used without particular limitation. To give an example of a typical production method, first, only propylene monomer is homopolymerized, then unreacted propylene monomer is removed, and then ethylene monomer or a mixed monomer of ethylene monomer and propylene monomer is charged and polymerization is carried out. can be mentioned. Further, the low density polyethylene is not particularly limited as long as it is an ethylene homopolymer or a random copolymer of ethylene and a different monomer such as propylene or butene-1 having a density of 0.930 or less, preferably 0.930 to 0.925. In particular,
Melt flow index (MFI) is 0.5g/10
min (at 190°C) or more, preferably 5 g/10 min (at 190°C)
190°C) or higher is preferable. Further, the high-density polyethylene is not particularly limited as long as it is an ethylene homopolymer or a random copolymer of ethylene and a different monomer such as propylene or butene-1 having a density of 0.94 or more. Among them, MFI is 3-30
g/10 min (at 190°C) high density polyethylene is preferred. In the present invention, in the mixture of P/E block copolymer, low density polyethylene and high density polyethylene, the content of low density polyethylene is 1 to 15% by weight, preferably 3 to 13% by weight, and the content of high density polyethylene is 1 to 15% by weight. , 1-30% by weight,
It is preferable to mix it in an amount of 5 to 25% by weight. Moreover, in this case, it is preferable to adjust the total of the two to 2 to 35% by weight of the mixture. Furthermore, known organic peroxides are generally used in the present invention. Typical organic peroxides include, for example, ketone peroxides such as methyl ethyl ketone peroxide and methyl isobutyl ketone peroxide; diacyl peroxides such as isobutyryl peroxide and acetyl peroxide; diisopropylbenzene hydroperoxide and other hydroperoxides. Oxide; Dialkyl peroxide such as 2,5-dimethyl 2,5-di-(t-butylperoxy)hexane, 1,3-bis-(t-butylperoxyisopropyl)benzene; 1,1-di-t -butylperoxy-cyclohexane, other peroxyketals; t-butylperoxyacetate,
Examples include alkyl peresters such as t-butyl peroxybenzoate; t-butyl peroxyisopropyl carbonate and other percarbonates. The amount of organic peroxide used is P/
0.001 to 1.0 for E-block copolymers, mixtures of low density polyethylene and high density polyethylene
Weight %, preferably 0.01 to 0.5 weight %, is common. As is clear from the Examples and Comparative Examples described below, the modified P/E block copolymer composition obtained by the method of the present invention maintains the mechanical properties originally possessed by P/E block copolymers to the extent that there is no problem in practical use. However, it has better optical properties, especially transparency, than the P/E block copolymer, and also has excellent impact whitening resistance.
Therefore, the P/E block copolymer can be suitably used as a material for various containers such as automobile batteries whose interiors must be seen through, and the fields of use of the P/E block copolymer can be further expanded. The modified polypropylene-ethylene block copolymer composition obtained by the method of the present invention may contain known additives such as antioxidants, heat stabilizers, ultraviolet absorbers, etc. EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples. In the Examples and Comparative Examples, the melt flow index (MFI), Izot impact strength, impact whitening degree, glossiness and haze were measured by the following methods. ΓMFI: Measured according to ASTM D-1238. ΓIzotsu impact strength; Nikko Ankelberg
63.6mm x 12.7mm by V22A-120 type injection molding machine
Create a test piece of ×0.31mm and pass ASTM D-256
Measured according to. Γ Impact whitening degree: 90mm x 60mm by the above injection molding machine
A test piece of ×2 mm was prepared. This test piece is 30mm
It was fixed on a steel plate cut out to the size of φ, and a 55g steel ball was dropped from a height of 2m into the center of the cutout.The test piece was left at 23℃ for 48 hours, and the steel ball was dropped at the point where the steel ball fell. The diameter of the whitened area was measured. In addition, the degree of whitening is determined from 1 to 1 with no whitening at all.
The evaluation was divided into 5 grades, with complete whitening being grade 5. Γ Glossiness: 60mm x 40mm x by the injection molding machine
A 3 mm test piece was prepared and measured according to ASTM D-523. Γ Haze: 90mm x 60mm x 1 by the injection molding machine
mm test pieces were prepared and measured according to ASTM D-1003. Further, the ethylene content in the P/E block copolymer was determined by infrared absorption spectrum. Example 1 Contains 4.9% by weight of ethylene moiety, MFI 1.6g/
Powdered P/E block copolymer for 10 minutes (at 230℃), density 0.955, pelletized high-density polyethylene for MFI 20g/10 minutes (at 190℃), density 0.918,
Pellet-like low density polyethylene with MFI of 45 g/10 minutes (at 190℃) was added to the mixture in Table 1.
2,5-dimethyl-2,5-(t-butylperoxy)-hexane (MBH) was added to the mixture as shown in Table 1, Furthermore, an antioxidant, a heat stabilizer, and a lubricant were added and mixed using a Henschel mixer. Next, Nakatani Kikai VSK40 with vent 40mmφ
The mixture was extruded using an extruder while controlling the resin temperature at the exit of the die to 230°C to obtain pellets of a modified P/E block copolymer composition. The composition was measured for MFI, haze, gloss, impact whitening, and Izod impact strength. Table the results.
It is also shown in 1.

[Table] Example 2 Pellets of a modified P/E block copolymer composition were obtained in the same manner as in No. 4 of Example 1 except that the low density polyethylene was replaced with the pelletized low density polyethylene shown in Table 2. Ta. The same measurements as in Example 1 were performed on this composition. The results are also shown in Table-2.

[Table] Example 3 Pellets of a modified P/E block copolymer composition were obtained in the same manner as in No. 4 of Example 1 except that the high density polyethylene was replaced with the pelleted high density polyethylene shown in Table 3. Ta. The same measurements as in Example 1 were performed on the composition. The results are also shown in Table 3.

[Table] Example 4 In No. 4 of Example 1, the type of organic peroxide was replaced with MBH, and 1,3-bis-(t-butylperoxy-isopropyl)benzene (BPB) was used.
Pellets of a modified P/E block copolymer composition were obtained in the same manner except that 1 and 1 and di-t-butyl peroxide (TBP) were used, respectively. The same measurements as in Example 1 were performed on this composition. The results are shown in Table 4.

[Table] Example 5 Propylene was polymerized at 60°C for 3 hours using a catalyst consisting of titanium trichloride and diethylaluminum monochloride. Next, unreacted propylene was purged, ethylene and propylene were supplied so that the gas phase molar concentration ratio was 1/4, and hydrogen gas was added to achieve a predetermined MI. The polymerization temperature during this time is
It was 50℃. The ethylene content in the polymer is 5
The mixed gas was continued to be supplied until the weight percentage was reached. The concentration of each gas was controlled by process gas chromatography.
After reaching a predetermined ethylene content, unreacted gas was purged, and then ethylene gas was supplied to continue polymerization to polymerize high-density polyethylene. Hydrogen gas was also supplied at the same time to achieve the specified MFI.
Ethylene gas was continued to be supplied until the total ethylene content in the polymer reached 20% by weight. Polymerization was terminated by purging unreacted gas and then adding methanol. catalyst and
After removing APP, a white powdery polymer was recovered. The ethylene content of the polymer is 221%,
The MI value was 2.2. The low density polyethylene used in Example 1 and the organic peroxide MBH were added to the polymer.
were mixed in the proportions shown in Table 5, and then using the same extruder as in Example 1 and under the same conditions, pellets of a modified P/E block copolymer composition were obtained. The composition was subjected to the same measurements as in Example 1. The measurement results are shown in Table-5. Furthermore, experiment No.
1 shows a comparative example.

[Table] Comparative Example 1 A blend of only the high-density polyethylene used in Example 1, a blend of only low-density polyethylene, and a blend containing no polyethylene at all with respect to the P/E block copolymer used in Example 1. The organic peroxide MBH was mixed in the ratio shown in Table 6, and an antioxidant, a heat stabilizer, and a lubricant were added to the mixture, and the mixture was treated in the same manner as in Example 1. I did this. The results are also shown in Table-6. Table 6 shows the measurement results for the P/E block copolymer used in Example 1 alone. In addition, MBH was added to the P/E block copolymer, high density polyethylene, and low density polyethylene of Example 1, respectively,
The pellets were pelletized in the same manner as in Example 1, and then mixed in the proportions shown in Table 6, and the same measurements were carried out. The results are also shown in Table-6.

[Table] *Those treated alone

Claims (1)

[Claims] 1. Propylene-ethylene block copolymer,
A method for producing a modified propylene-ethylene block copolymer composition, which comprises heat-treating a mixture of low-density polyethylene and high-density polyethylene in the presence of an organic peroxide. 2 The mixture contains 1-15% by weight of low-density polyethylene
and 1 to 30% by weight of high-density polyethylene. 3 The amount of organic peroxide used relative to the mixture
The method according to claim 1, wherein the amount is 0.001 to 1% by weight.