JPH07107111B2 - Polyolefin composition with improved stability - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel polyolefin composition having improved stability, and more specifically, to a specific phosphite-based compound, phosphonite-based compound, and phenolic compound, and a fatty acid metal in the polyolefin. The present invention relates to a polyolefin composition obtained by adding a salt and hydrotalcite and having improved color stability, heat stability and corrosion resistance.

(Prior Art) Regarding the stability of pellets or molded articles made of polyolefin, first, yellowing during long-term storage and deterioration during heating must be taken into consideration. It is not always easy to take measures to solve both problems, and in order to prevent deterioration during heating, phenolic antioxidants such as 3,5-di-t
It is a well known fact that the addition of ert-butyl-4-hydroxytoluene (BHT) causes yellowing during long-term storage.

In recent years, the use of highly active catalysts has led to the production of polyolefins by a so-called deashing process, in which the catalyst removal step is omitted, but it is said that the catalyst residue remaining in the polymer, especially titanium, promotes various types of deterioration. There is.

Furthermore, a chlorine compound remains as a catalyst residue in a polyolefin produced by a deashing process, and it has been pointed out that this chlorine compound corrodes metals such as a molding machine when melt-processing the polyolefin. . A fatty acid metal salt is usually added to prevent corrosion due to a chlorine compound, but the metal salt has a drawback that its anticorrosive effect is lost when a phosphorus compound, particularly a phosphite-based compound, coexists as an antioxidant. Thus, in selecting an antioxidant, it is necessary to consider the influence on the anticorrosion effect.

It is known to use a phenol-based and a phosphite-based antioxidant together to prevent heat deterioration. For example, Japanese Patent Publication No. 56-5417 discloses a combination of a trisaryl phosphite and a phenol-based antioxidant. Is listed. However, these combinations cannot prevent yellowing during long-term storage and thermal deterioration during high temperature molding.

In addition, a method of using a specific organic phosphite compound in combination with an alkyl-substituted phenolic stabilizer has been reported in order to solve yellowing during long-term storage (Japanese Patent Publication No. 56-2593).
No. 5), it is difficult to say that its preventive effect is still sufficient, and when it is applied to a polyolefin produced by a deashing-free process, the problem of corrosion cannot be avoided.

Further, in JP-A-61-14240, at least one phosphorus compound selected from phosphite, phosphonite and phosphonic acid derivatives and a phenolic antioxidant having a molecular weight of 400 or more are blended with linear low density polyethylene. Although the method is described, even these combinations are not always sufficient to prevent yellowing during long-term storage, and there is a problem in terms of measures against corrosion.

JP-A-61-133251 describes a composition in which a phenolic antioxidant, di (alkyl or aryl) pentaerythritol diphosphite and hydrotalcite are combined. Although the corrosion due to chlorine compounds can be prevented by mixing hydrotalcite, with the above combination, the yellowing preventing effect decreases during long-term storage and under high temperature conditions, and the resin tends to be colored brown easily when melted.

(Problems to be Solved by the Invention) The present invention selects a combination of additives suitable for polyolefins, particularly polyolefins produced by a deashing-free process, and uses them to prevent yellowing during long-term storage and deterioration during heating. An object of the present invention is to provide a polyolefin composition which is prevented and has reduced metal corrosiveness.

(Means for Attempting to Solve the Problem) As a result of intensive studies conducted by the present inventors in accordance with the above objects, they found that a polyolefin composition satisfying the above objects can be obtained by using five specific additives. It was

That is, the present invention provides a polyolefin composition having improved stability, which comprises the following additives added to the polyolefin.

(I) Pentaerythritol diphosphite represented by the following formula (R _1, R _2: an aryl group) (ii) tetrakis (2,4-di -tert- butylphenyl)
4,4'-biphenylene diphosphonite (iii) 3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionic acid ester (iv) fatty acid metal salt (v) hydrotalcites The polyolefin used in the present invention is medium / low density polyethylene, high density polyethylene, polypropylene, poly 1-
In addition to homopolymers such as butene, alternating copolymers of α-olefins such as ethylene, propylene, 1-butene, 1-hexene and 4-methyl-1-pentene and ethylene-vinyl acetate copolymers, ethylene-acrylic acid Examples thereof include ethyl copolymers. In particular, remarkable effects are exhibited when the above-mentioned polymers which are polymerized with a highly active Ziegler type catalyst and have not undergone the catalyst removing step, so-called deashing step, are used.

Among the additives used in the present invention, specific examples of (i) pentaerythritol diphosphite include dibenzyl
Pentaerythritol diphosphite, bis (2,4-
Di-tert-butylphenyl) pentaerythritol diphosphite, bis (2-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol. Examples thereof include diphosphite and bis (2-cyclohexylphenyl) pentaerythritol diphosphite, but especially bis (2,4-di-tert.
-Butylphenyl) pentaerythritol diphosphite and bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite are preferred.

Among the additives used in the present invention, (ii) tetrakis (2,4
-Di-tert-butylphenyl) 4,4'-biphenylene
Diphosphonite alone shows only the same yellowing-preventing effect as the various phosphites of (i) above, but it has been found that when used in combination with the phosphonite, it exhibits an excellent yellowing-preventing effect due to a synergistic effect. It was the one.

Among the additives used in the present invention, (iii) 3- (3 ', 5'
Examples of the ester of -di-tert-butyl-4'-hydroxyphenyl) propionic acid include pentaerythritol tetrakis [3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate] and Octadecyl 3- (3 ', 5'-di-tert-butyl-
4'-hydroxyphenyl) propionate and the like.

Among the additives used in the present invention, (iv) fatty acid metal salts include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, and other fatty acids, and lithium, sodium, magnesium, and calcium. , And salts with metals such as zinc, but calcium stearate is particularly preferable.

Among the additives used in the present invention, (v) hydrotalcites are double salt compounds represented by the following formula.

(M ²⁺ ) _1-x A1 _x (OH) ₂ (A ^n- ) _{x / n}・ mH ₂ O (where 0 <x ≦ 0.5, m: real number, M ²⁺ : Mg, Ca or Zn, A
^n-: Although both used for natural products and synthetic products as n-valent anion) This compound, in particular M ²⁺ is Mg, A ^n-is ▲ CO ^2- ₃ ▼ a is synthetic is preferred.

The blending composition of the above components used in the present invention is such that the additives (i) and (ii) are both 0.005 to 0.2 parts by weight, preferably 0.01 to 0.15 parts by weight, and the additives (iii ) Is 0.005-0.15 parts by weight, preferably 0.
01-0.08 parts by weight, additive (iv) 0.01-0.25 parts by weight, preferably 0.02-0.15 parts by weight, additive (v) 0.01-0.1 parts by weight
Parts by weight, preferably 0.02 to 0.08 parts by weight.

If the amount of the additive (i) is less than 0.005 part by weight, yellowing during long-term storage is unavoidable, while if it exceeds 0.2 part by weight, the generation of rust increases. The amount of additive (ii) is 0.005
Yellowing during storage for a long period of time is unavoidable even when the amount is less than 10 parts by weight, and on the other hand, the effect is not improved even when the amount exceeds 0.2 parts by weight. When the amount of the additive (iii) is less than 0.005 parts by weight, deterioration during heating is not suppressed, while when it exceeds 0.15 parts by weight, yellowing during long-term storage is promoted. The amounts of the additives (iv) and (v) are closely related to each other, and when the amount of the additive (iv) is less than 0.01 parts by weight, the amount of the additive (v) is considered in view of anticorrosion effect. Is more than 0.1 part by weight, which results in the progress of coloring under high temperature conditions, which is not preferable. When the amount of the additive (v) is less than 0.01 parts by weight, the anticorrosive effect is adversely affected even when the amount of the additive (iv) alone is increased in combination with the phosphorus-based antioxidant, especially the phosphite-based antioxidant. This tendency is remarkable when the amount decreases and exceeds 0.2 parts by weight.

Any known technique can be used as a method for producing the composition according to the present invention. A typical example is a method in which the above-mentioned five components are dry-mixed, and then the blend is mechanically melt-kneaded. For kneading, a single-screw or twin-screw extruder, various kneaders and the like can be used.

In the present invention, in addition to the above five components, if necessary, an antistatic agent, a lubricant, an ultraviolet absorber, a light stabilizer, a nucleating agent, a flame retardant, an anti-blocking agent, a foaming agent, a filler, a pigment and the like. You may mix an additive.

(Effect of the invention) The polyolefin composition obtained by the present invention has significantly improved color stability, thermal stability and corrosion resistance, and in particular, when it is applied to a polyolefin produced by a deashing process, It is possible to provide a composition having a great improvement in stability or resistance to yellowing during long-term storage, deterioration during heating or melting, metal corrosion, etc. It was

(Examples and Comparative Examples) Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited thereto. The properties were measured in the examples and comparative examples by the following methods.

(Color stability) Pellets or molded articles were subjected to an accelerated test for estimating the degree of yellowing during long-term storage. That is, a press sheet with a thickness of 2 mm prepared from the prepared composition was heated at a temperature of 80
After exposing it in a thermo-hygrostat at ℃ and 90% relative humidity for 2 weeks,
The yellowness (according to JIS K7103) was measured.

(Thermal stability) As a guideline for the thermal stability of the molded product, use the above-mentioned sheet at 120 ° C.
Yellowness was measured after 10 days of exposure in an oven.
This is the heating yellowness.

Further, as a measure of thermal stability when melt-kneading the composition,
The change in torque corresponding to the change in viscosity during kneading was measured.
That is, the prepared composition was kneaded at 210 ° C, 40 rpm using Labo Plastomill manufactured by Toyo Seiki Co., Ltd., and for polyethylene, the time until the change in torque was observed (min) was measured, and polypropylene was used. About 20min
The reduction rate (%) of the torque after kneading was measured. These are referred to as heat deterioration degrees.

(Corrosion resistance) The prepared composition is heated to 250 ℃ and melted, the soft iron plate is immersed in it for 2 hours, the composition adhering to it is removed and then the temperature is 80 ℃ and the relative humidity is 100%. The amount of rust generated after 20 hours of exposure to the atmosphere was determined by the weight increase rate. 1% or less is represented by O, 4% or more is represented by X, and the middle of the two is represented by Δ.

Examples 1 to 4 The components used are as follows.

Polyolefin: (A) Ethylene / 1-butene copolymer (powder, MFR 18, density 0.942 g / cm ³ , Ti residual amount 9 ppm) Additive (i): (D) Bis (2,4-di-tert. -Butylphenyl) pentaerythritol diphosphite (trade name: Ultranox 626, manufactured by BorgWarner) (E) bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite (trade name: Mark PEP36, manufactured by Adeka Argus Chemical Co., Ltd. Additive (ii): (H) Tetrakis (2,4-di-tert-butylphenyl)
4,4'-biphenylene diphosphonite (trade name: Irgaphos P-EPQ, manufactured by Ciba Geigy) Additive (iii): (I) Pentaerythritol tetrakis [3-
(3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate] (Product name: Irganox 1010, manufactured by Ciba Geigy) Additive (iv): (L) Calcium stearate Oxidizing agent (v): (M) Hydrotalcite (Brand name: DHT-4A, Kyowa Chemical Industry Co., Ltd.) Mg _0.7 Al _0.3 (OH) ₂ (CO ₃ ) _0.15 0.5H ₂ O After dry blending, a 40 mmφ extruder was used to granulate the composition at a resin temperature of 150 ° C., and a sample was prepared using this, and various property tests were conducted. The results are shown in Table 1.

Comparative Examples 1 to 15 In addition to using (D) bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite as the additive (i), the following phosphite compounds were also used in Examples 1 to 1 The same components as in Example 3 were used, and the same composition as shown in Table 1 was applied to the composition. Table 1 shows the results of a property test conducted using this.

Additive (i): (F) Tris (2,4-di-tert-butylphenyl) phosphite (trade name: Irgaphos 168, manufactured by Ciba-Geigy) (G) Distearyl pentaerythritol diphosphite (trade name: Weston 618, manufactured by BorgWarner) Examples 5 and 6, Comparative Examples 16 to 19 As the polyolefin and the additive (iii), (A) ethylene / 1-butene copolymer and (I) pentaerythritol tetrakis [3- ( 3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate], except that the following compounds were used, respectively.
A composition was obtained by using the same components as those in No. 3 and treating the compounding compositions shown in Table 2 in the same manner as in the above-mentioned Examples. Table 2 shows the results of a property test conducted using this.

Polyolefin: (B) High-density polyethylene (powder, trade name: Stafrene E809 (M), manufactured by Nippon Petrochemical Co., Ltd.) Additive (iii): (J) Octadecyl-3- (3 ', 5'-di -Tert-butyl-4'-hydroxyphenyl) propionate (trade name: Irganox 1076, manufactured by Ciba-Geigy) (K) 3,5-di-tert-butyl-4-hydroxytoluene (BHT) Example 7, Comparative Example The following are used as the polyolefin instead of the (A) ethylene / 1-butene copolymer, and (I) pentaerythritol tetrakis [3-] as the additive (iii).
(3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate], except that the above (K) 3,5-di-tert-butyl-4-hydroxytoluene (BHT) is used. The same components as in Examples 1 to 3 were used, and the same composition as shown in Table 2 was used to carry out the same treatment as in the above Examples to obtain compositions. Table 2 shows the results of a property test conducted using this.

Polyolefin: (C) Polypropylene (powder, trade name: Nisseki Polypro J725N, manufactured by Nippon Petrochemical Co., Ltd.) The polyolefins used in the above Examples and Comparative Examples were both polymerized using a highly active Ziegler type catalyst. And, it has not undergone the decalcification process.

As is clear from the results shown in Tables 1 and 2, the polyolefin compositions of Examples 1 to 7, which are within the scope of the present invention, are excellent in color stability, heat stability (heat yellowness and heat deterioration) and rust inhibition. It showed good performance and improved stability. On the other hand, in Comparative Examples 1 to 21, which are out of the scope of the present invention, it is difficult to improve the above properties in a well-balanced manner, and it is understood that the stability is poor.

Explanation of symbols in the table: A: ethylene / 1-butene copolymer ethylene B: high-density polyethylene <STAFREN E809 (M)> C: polypropylene <Nisseki Polypro J725N> D: bis (2,4-di-tert- Butylphenyl) pentaerythritol diphosphite <Ultranox 626> E: Bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite <Mark P
EP36> F: Tris (2,4-di-tert-butylphenyl) phosphite <Irgafos 168> G: Distearyl / pentaerythritol / diphosphite <Weston 618> H: Tetrakis (2,4-di-tert-butylphenyl) ) 4,4 ′
-Biphenylene diphosphonite <Irgafos P-EP
Q〉 I: Pentaerythritol tetrakis [3- (3 ′, 5 ′
-Di-tert-butyl-4'-hydroxyphenyl) propionate] <Irganox 1010> J: octadecyl 3- (3 ', 5'-di-tert-butyl-
4'-hydroxyphenyl) propionate <Irganox 1076> K: 3,5-di-tert-butyl-4-hydroxytoluene <B
HT> L: Calcium stearate M: Hydrotalcite <DHT-4A>

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area // (C08K 13/02 3:26 5: 098 5:13 5: 527 5: 5393)

Claims (5)

[Claims] 1. A polyolefin composition with improved stability, wherein the polyolefin comprises the following additives: (I) Pentaerythritol diphosphite represented by the following formula (R _1, R _2: an aryl group) (ii) tetrakis (2,4-di -tert- butylphenyl)
4,4'-biphenylene diphosphonite (iii) 3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionic acid ester (iv) fatty acid metal salt (v) hydrotalcites 2. The polyolefin composition with improved stability according to claim 1, wherein the polyolefin is polymerized using a highly active Ziegler-based catalyst and has not undergone a deashing step. 3. The (1) pentaerythritol diphosphite wherein R ₁ and R ₂ are both 2,4-di-ter
t-butylphenyl group or 2,6-di-tert-butyl-4
A polyolefin composition with improved stability according to claim 1, which is a methylphenyl group. 4. The ester of (iii) is pentaerythritol tetrakis [3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate] or octadecyl 3- (3', 5). ′ -Di-tert-butyl-
A polyolefin composition with improved stability as claimed in claim 1 which is 4'-hydroxyphenyl) propionate. 5. The polyolefin composition with improved stability according to claim 1, wherein the metal salt of the fatty acid (iv) is calcium stearate.