JPS6069105A - Modification of crystalline polypropylene - Google Patents

Abstract

PURPOSE:To obtain modified PP excellent in heat stability and good in the color of a molding, by mixing crystalline PP with a specified radical scavenger and a specified peroxide-decomposing agent and heating the mixture in the presence of an organic peroxide. CONSTITUTION:Crystalline PP is mixed with (A) a hindered phenol radical scavenger (e.g., 2,6-di-tert-butyl-4-methylphenol) and (B) a phosphite peroxide-decomposing agent [e.g., cyclic neopentanetetraylbis(octadecyl phosphate)] so that the total amount of agents A and B is 0.03-0.3pts.wt. per 100pts.wt. PP and the molar ratio of the hindered phenol groups of agent A to the phosphite groups of agent B is 50/50-30/70, and the mixture is heated in the presence of an organic peroxide, e.g., 2,5-dimethyl-2,5-di-(tert-butyl-peroxy)hexane, to modity the PP. It is possible to obtain easily modified PP having excellent heat stability and providing a molding of an excellent color.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for modifying crystalline polypropylene that can easily yield modified polypropylene that has excellent thermal stability and provides molded articles with excellent hue.

When crystalline polypropylene is heat-treated in the presence of an organic peroxide, high molecular weight components that have a negative effect on melt fluidity are moderately degraded, resulting in a modified polypropylene with a narrow molecular film distribution. It is already known that modified polypropylene has excellent moldability, is not cumbersome, and can improve the physical properties of molded products (Tokuko Sho J'/
-t, tgi riwo issue and special public show! 2-/ri, J-93 Publication).

However, in order to use such modified polypropylene for molding, an antioxidant, most commonly a phenolic radical scavenger, is added to prevent thermal decomposition during melting. The molded products obtained by blending the above had the disadvantage that they were colored yellow and their commercial value was significantly reduced.

If such a molded product is molded without adding the same radical scavenger to prevent coloring, thermal decomposition will occur during heating and melting during molding, and the physical properties of the molded product (for example, impact resistance) will occur. This results in a significant deterioration in properties (elongation, tensile strength, etc.).

The present inventors have conducted various studies to improve the above-mentioned drawbacks of conventional methods for modifying crystalline polypropylene.
A mixture of a hindered phenol-based radical scavenger and a phosphite-based peroxide decomposer in a specific ratio is added to crystalline polypropylene in a specific ratio, and then subjected to heat denaturation treatment. In other words, they have discovered that the object can be easily achieved, and have arrived at the present invention.

That is, in the method for modifying crystalline polypropylene of the present invention, when modifying crystalline polypropylene by heat treatment in the presence of an organic peroxide, a hindered phenol radical scavenger and a phosphor are added to the heat-treated polypropylene. phyto-based peroxide decomposer in a ratio where the total amount of both is 0.03 to 0.3 parts by weight based on 100 parts by weight of polypropylene, and the hindered phenol of the hindered phenol-based radical scavenger. The molar ratio of the group to the phosphite group of the phosphite-based peroxide decomposer is J-07
! This method is characterized by blending in a ratio of 0 to 30/70.

The crystalline polypropylene in the present invention can be produced by using a so-called Ziegler-Natsuta catalyst to produce propylene alone or having propylene as the main component, with a relatively small amount of other α- Polymerization (including copolymerization) of an α-olefin mixture containing an olefin (e.g., ethylene, butene/, hexene/, octene/, goomethylpentene, etc.) as a -s monomer.
It is a crystalline propylene-based polymer obtained by In the case of copolymers, if the 3-comonomer is ethylene, the ethylene content is 7.
It is 5 mol% or less, preferably 7 mol% or less.

The hindered phenol radical scavenger in the present invention is a phenol radical scavenger in which a bulky substituent is placed near the phenolic hydroxyl group to stabilize the radical after it is captured. Specific examples thereof include co,t-tert-butyl-g-methylphenol 1
．． 2.4t-dimethyl-6-tert-butylphenol, 3
-Tertiary butyl-gu-hydroxy ayusol 1.2.6-
Dioctadecyl-p-cresol 1.2,4t-dumedel-l-isobonylphenol, 2. A-diisobonyl-p-cresol, n-octadecyl-β-(lI'-
Hydroxy-3',jfl-di-tert-butylphenol) propionate, styrenated phenol, dimethyl-6-α-methylcyclohexylphenol, Hiroshi, 4'/-phthyritin-bis(3-methyl-tert-butylphenol) −−＋− le), Hiro, ≠′-methylenebis(,2,i4-di-tert-butylphenol, j,,2/-methylenebis(6
-tert-butyl-p-cresol), co-1,2'-methylene-bis(, g-g tert-butyl-guethylphenol)
, alkylated bisphenol, co, 6-bis(2!-hyde gastric 3/-tert-butyl-!-methylbenzyl)
-l-Methylphenol, tris(,2-/thiru-hydroxy-j-tert-butylphenyl)butane, tetrakis-[methylene-(J,J--di-tert-butyl-
l-hydroxy-hydrocinnamate)] methane, hydroquinone monobenzyl ether, p, p'-
Thiobis (tert-butyl-m-cresol), tips.

2I-thiopis(gumethyl-6-tert-butylphenol), bis(,2-hydroxy-3,!-di-tert-butylphenyl)sulfi)',! , 2/-methylenebis(coumethyl-A-α-methylcyclohexylphenol), /.

! , J-) Remethylluco J, 6-tris(,!,,3:
-di-tert-butyl-g-hydroxypenzyl)benzene, 2,4t-bis(≠-hydroxy-3,3-
di-tert-butylphenolic)-A-(n-octylthio)-/, 3.3-) riazine, 6-(t-hydroyloxy-3,3-di-tert-butylanilino)-,2,
44-bis(n-octylthio) -/, 3. j-triazine, (t-hydroxy-3,J'-di-tert-butylbenzyl)-dioctadecyl phosphate, phosphorus-alkylated phenol condensate, tetrakis[methylene-3-(3,!-di-tert-butylbenzyl) Examples include butyl-buty-tetraxyphenyl)butybionate]methane.

Examples of the phosphite-based peroxide decomposer in the present invention include triphenyl phosphite, trisnonylphenyl phosphite, diphenyldecyl phosphite,
Examples include phenyldidecyl phosphite, tridecyl phosphite, trilauryltrithiophosphite, triotadecyl phosphite, cyclic neopentanetetrayl bis(octadecyl phosphite), and the like.

The organic peroxide used in the present invention should not have a decomposition temperature that is too low for uniform modification;
Preferably, the half-life in OC is 2 hours or more. For example, 2,j-dimethyl-2,j-di(tert-butylperoxy)hexane 1.2. J-dimethylco,! −
Dialkyl peroxides such as di-(tert-butyl peroxy)hexyne, peroxy esters such as tert-butyl peroxy isopropyl carbonate, peroxy such as n-7' thirug, goobis (tert-butyl peroxy) valerate, etc. Examples include ketals.

In the present invention, the ratio of the hindered phenol radical scavenger and the phosphite peroxide decomposer is determined by The molar ratio of phyto groups is 307. ! ! 'The ratio must be between 0 and 30/70. The same molar ratio is 307. If the force is higher than tO, the molded product will become colored and its commercial value will decrease.

Furthermore, when the molar ratio is lower than 30,770, thermal stability decreases, resulting in a decrease in physical properties such as impact resistance.

In addition, the total usage ratio of the hindered phenol radical scavenger and the phosphite peroxide decomposer in the present invention is 0 to 100 parts by weight of crystalline polypropylene.
．． 0.3 to 0.3 parts by weight. If the proportion used is too small, the thermal stability of the modified polypropylene and the hue improvement effect of the molded product cannot be obtained, and if the proportion used is too high, the above-mentioned improvement effect commensurate with that cannot be obtained. , there is no economic benefit.

The proportion of organic peroxide used in the present invention is preferably 0.00 to 0.03 parts by weight per 100 parts by weight of crystalline polypropylene.

The preferred heat denaturation treatment temperature in the present invention is /70~.
The temperature is 210C, and the preferable heat denaturation treatment time is 30 seconds to 2≠θ seconds. If the thermal modification treatment temperature is too low, the polypropylene will not melt sufficiently, and the decomposition of the organic peroxide will be slow, resulting in insufficient modification.
As a result, for example, the load on the extruder increases in the subsequent granulation step of modified polypropylene, and the effects of improving the moldability of modified polypropylene and the physical properties of molded articles cannot be obtained. In addition, if the thermal denaturation treatment temperature becomes too high, the decomposition of the organic peroxide will occur rapidly, resulting in uneven denaturation and more thermal deterioration of polypropylene than necessary, resulting in poor quality of the molded product. Inconveniences such as a decrease in impact resistance occur.

Various devices can be used to carry out the heat treatment in the present invention, but it is generally convenient to use a screw extruder with a set of heating cylinders, such as those used in granulation processes. . Using such a screw extruder, crystalline polypropylene mixed with a predetermined amount of organic peroxide, a hindered phenol radical scavenger, a phosphite peroxide decomposer, etc. is continuously supplied to the extruder. However, it may be continuously extruded while heating, melting, and kneading under conditions such that heat treatment is performed at a predetermined temperature for a predetermined time. Further, for example, a twin-screw kneader or the like may be provided upstream of such a screw extruder, and preliminary heat-melting mixing treatment may be performed using the twin-screw kneader or the like.

In addition to the above-mentioned various additives, the crystalline polypropylene to be subjected to the heat modification treatment of the present invention may further contain fillers, ultraviolet absorbers, pigments, antistatic agents, molding aids, etc. as necessary. It can be blended with.

According to the modification method of the present invention, in addition to obtaining the same physical property improvement effect as in the modification of ordinary crystalline polypropylene, the modified polypropylene obtained particularly has excellent thermal stability compared to ordinary modified polypropylene, Moreover, the unique and excellent effect that the hue of the molded product is extremely good can be achieved.

Next, the present invention will be explained in further detail by giving Examples and Comparative Examples. "Parts" in these examples are based on weight unless otherwise specified.

Example/Crystalline polypropylene 10 containing 5% by weight of ethylene
0 parts, 0.03 parts of 1-tert-butyl-t-methylphenol of the formula, 0.03 parts of cyclic neobentanete-//- lylbis(octadecyl phosphite) of the formula. /Part 1.2. J'-dimethyl-λ,! -0.003 parts of di(tert-butylperoxy)hexane, and 0.003 parts of calcium stearate. / part mixed, diameter 410 mm, L
/D=, 2jf) Using a single-screw extruder with a screw, the mixture was extruded and granulated while heating and melt-kneading at zooc temperature to obtain modified polypropylene pellets.

In this case, the residence time of the charged material in the heating zone of the extruder was 120 seconds. In addition, the molar ratio between the phenol group of λ,6-di-tert-butyl-t-methylphenol and the phosphite group of cyclic neopentanetetrayl bis(octadecyl phosphite) (hereinafter referred to as the "functional group ratio") ) was 33/l, 7.

Example/Example/In. A modified polypropylene was produced in the same manner as in Example 1, except that the amount of 2.6-di-tert-butyl-gu-methylphenol was changed to O,OS parts.

Note that the functional group molar ratio in this case was l/J'4Z.

Comparative Example/The amount of cyclic neopentanetetrayl bis(octadecyl phosphite) used was 0 parts, and the amount of 2,6-di-tert-butyl-gumethylphenol was 0. /
Modified polypropylene was produced in the same manner as in Example 1, except that the modified polypropylene was changed to 0 parts.

Comparative Example C2, A - The amount of di-tert-butyl-goomethylphenol used was 0.7 parts, and the amount of cyclic neopentanetetrayl bis(octadecyl phosphite) used was 0.0 parts.
Modified polypropylene was produced in the same manner as in Example except that 3 parts were used.

In addition, the functional group molar ratio in this case was ♂j//j.

Comparative Example 3 The amount of co,t-di-tert-butyl≠-methylphenol used was 7o,
A modified polypropylene was produced in the same manner as in Example 1, except that the os part was changed.

The molar ratio of the functional groups in this case was 1:2 parts: 3 g.

Comparative Example 2. A modified polypropylene was produced in the same manner as in Example 1, except that the amount of 6-di-tert-butyl-gu methylphenol used was changed to 0 parts.

Example 3 In place of 2,t-di-tert-butyl-gumethylphenol, tetrakis[methylene-3-(3,3-'
) ta tridibutyl≠-hydroxyphenyl)propionate cometaf 0.03 part was used, and the amount of cyclic neopentanetetrayl bis(octadecyl phosphite) was changed to 0.01 part, otherwise the procedure was carried out. example/
Modified polypropylene was produced in the same manner as above.

In addition, the functional group molar ratio in this case was 31/1.2.

Comparative example! A modified polypropylene was produced in the same manner as in Example 3 except that the amount of cyclic neopentanetetrayl bis(octadecyl phosphite) used was changed to 0.03 part.

In addition, the functional group molar ratio in this case is J-j/II J-
Met.

The modified polypropylene obtained in each of the above Examples and Comparative Examples was tested for hue of pellets and molded products, and thermal stability. The results were as shown in Table 7.

In addition, each of these test methods and their evaluation is 1/j- The details are as follows.

(1) Molded product hue test and evaluation of each modified polypropylene beret obtained on each side]・
using a water-cooled inflation molding machine (Model DTK-80 manufactured by Yoda Seisakusho, screw diameter 39 mm, screw L
/D=23, die diameter/zap Q mm, die slit gap/, Qmm), and the thickness is 70μ at a temperature of 2IOC.
A film was formed.

The obtained film was punched out into a square lIOmm x lsOmm, stacked in a bundle with a thickness of lQmm, and the 110 m
Using the reflected light from a surface of m x 170 mm, JIS-
The degree of yellowness was measured and evaluated according to the method of 7103.

Note that when the measured value of yellowness is +47 or more, yellow color is clearly recognized even with the naked eye, and the commercial value is extremely low.

(11) Hue test and evaluation of pellets The yellowness of the modified polypropylene pellets obtained on each side was measured in accordance with JIS-7103.

(fil) Thermal stability test and evaluation The modified polypropylene pellets obtained on each side were
Using an extruder with a Qmm screw, 2! O.C.
The MFR of each pellet obtained by repeated extrusion three times at a heating temperature of (hereinafter referred to as "MFR'J") and the MFR of each modified polypropylene pellet before extrusion.
(hereinafter referred to as l'-MFR'J) is AS
It was measured in accordance with the test method of TM-DI237-73, and thermal stability was evaluated based on the ratio of MFR'/MFR'.

In addition, the assimilation value is preferably /, J' or less in order to ensure good moldability of the modified polypropylene and physical properties of the molded article.

table / Patent applicant: Mitsubishi Chemical Industries, Ltd. -/Taichi

Claims (1)

[Claims] /) When heat-treating and modifying crystalline polypropylene in the presence of an organic peroxide, a hindered phenol-based radical scavenger and a phosphite-based peroxide are added to the heat-treated polypropylene. and a decomposing agent, the total amount of both of which is 0.03 to 0.3 based on 100 parts by weight of polypropylene.
In terms of parts by weight, the molar ratio of the hindered phenol group of the hindered phenol radical scavenger to the phosphite group of the phosphite peroxide decomposer is !
A method for modifying crystalline polypropylene, which comprises blending in a ratio of 0/jtO to 30/70. , 2) The organic peroxide is 0.00/-0.003 parts by weight per 100 parts by weight of polypropylene, and the heat treatment temperature is /70-. 8. The method according to claim 7, which is 2ZOC.