JP2907532B2 - Thermoplastic resin composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a titanium oxide-containing polyethylene resin composition having yellowing prevention performance and excellent whiteness.

2. Description of the Related Art Thermoplastic resins are used in a wide range of fields, from industrial parts to household goods, but are used in various colors from the viewpoint of aesthetics, light-shielding properties, and reflectivity. At this time, titanium oxide is often used as the pigment. Particularly, in a field where high reflectance (whiteness) and hiding power are simultaneously required, a large amount of titanium oxide needs to be added. However, since titanium oxide has a high surface activity, when it is blended in a thermoplastic resin, the light resistance, heat resistance, and the like of the thermoplastic resin are reduced, and the thermoplastic resin becomes yellowish.

Further, in order to maintain thermal stability in a molding machine and thermal stability over time, various kinds of thermal stabilizers such as phenolic and phosphorous are generally added to thermoplastic resins and used.
55-142335, JP-A-57-143351, JP-A-2-8838).

Problems to be Solved by the Invention A thermoplastic resin containing titanium oxide also yellows, but those further added with a phenolic heat stabilizer as an antioxidant show severe yellowing.

Even when a phosphorus-based antioxidant is added, or when a plurality of antioxidants are added and the selection of the antioxidant is not appropriate, problems such as yellowing and thermal stability remain. In particular, when light resistance and heat resistance tests are performed, a remarkable deterioration phenomenon does not occur in a short time, but a problem occurs in a long time of about 98 hours.

When the amount of the antioxidant is increased, the light resistance and the heat resistance may be considerably improved.However, the amount of deposits on the inner wall of the die at the time of molding extrusion increases, and the smoothness of the surface of the molded product is improved. It will be damaged.

Therefore, an object of the present inventor is to solve the above problems of yellowing, thermal stability and the like, with a polyethylene resin composition containing titanium oxide.

Means for Solving the Problems The present inventor has conducted various studies to achieve the above object,
A polyethylene resin composition characterized in that a phenol-based and phosphorus-based antioxidant and a metal carboxylate are added to a titanium oxide-containing polyethylene resin.

Examples of the thermoplastic resin used in the present invention include polyethylene.

The titanium oxide is not particularly limited, and a general commercial product can be used arbitrarily.

More preferred titanium oxide is one whose surface is treated with an aluminum compound, a silicon compound, a zinc compound or an organic compound (Japanese Patent Laid-Open No. 55-15 / 1979).
4317). Since the titanium oxide surface-treated in this way has an active titanium oxide surface covered with these compounds and the like, the deterioration and deterioration of the polyethylene resin are prevented or at least reduced, and the prevention and reduction by the antioxidant are prevented. Role can be minimized.

The content of titanium oxide is 5 to 250 parts by weight based on 100 parts by weight of the polyethylene resin, particularly when optical characteristics such as high reflectance (whiteness) and concealing property are important. If the content is less than this, sufficient whiteness, hiding power, etc. cannot be obtained,
In addition, when the content exceeds this, it becomes difficult to produce the polyethylene resin composition, and in kneading and extrusion or various molding steps, or the obtained molded product, for example, the strength of the film is significantly reduced, and it is difficult to form a film. Becomes

The average center diameter of the titanium oxide fine powder used is 0.
01 to 10 μm, 0.05 to obtain particularly high optical characteristics
0.5 μm is desirable.

Next, the phenolic antioxidant used in the present invention is mono-type 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, stearyl propionate-β- (3,5-di- 2,2'-methylene-bis (4-methyl-6-t-butylphenol), 4,4'-, such as t-butyl-4-hydroxyphenyl)
1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane as a polymer type such as butylidene-bis (3-methyl-6-t-butylphenol);
Tetrakis [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane and the like, but one-sided hindered phenol A: 3,9-bis [2- [ 3- (3-t-butyl-4-hydroxy-5-methylphenyl) -propionyloxy]
-1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane B: 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate C: triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] And the like.

Examples of the phosphorus-based antioxidant used in the present invention include: a: bis (2,6-di-t-butyl-4-methylphenyl) -pentaerythritol diphosphite B: Tetrakis (2,4-di-t-butylphenyl) 4,4 '
-Biphenylene phosphite C: Tris (2,4-di-t-butylphenyl) phosphite Etc.

Next, the metal salt of a carboxylic acid used in the present invention may be a metal salt of a fatty acid such as stearic acid or barmitic acid, or a metal salt of a cyclic carboxylic acid such as naphthenic acid.As the metal of the metal salt, Zn, Al , Ca, Cu, Pb, Ni, Ba, Mg and the like.

In the present invention, two or more of each of these phenol-based and phosphorus-based antioxidants and metal carboxylate may be added and used.

 Next, appropriate amounts of these additives will be described.

The phenolic antioxidant should be added in an amount of 0.001 to 0.5 part by weight, the phosphorus antioxidant in an amount of 0.001 to 1 part by weight, and the metal carboxylate in an amount of 1.0 to 10 parts by weight based on 100 parts by weight of the polyethylene resin. desirable.

If the addition amount is less than the above, there is no effect on the improvement of light resistance and heat resistance. Particularly in the case of a metal carboxylate, the kneading operation of the polyethylene resin composition becomes difficult in addition to these effects. Further, when the amount exceeds the above-mentioned amount, the effect is not further improved, and it is economically wasteful, and in some cases,
In a step after the use of the thermoplastic resin composition, for example, there may be a case where a die lip stain or the like during melt extrusion is adversely affected.

When two or more phenol-based and phosphorus-based antioxidants and two or more metal carboxylate salts are added, the total amount of each of them is preferably within the above range.

In the present invention, when the polyethylene resin composition is obtained, it is dry-blended in advance. The mixing method is not particularly limited, and any mixing device such as a Henschel mixer can be used as long as mixing is sufficient.

Also, polyethylene resin, titanium oxide, antioxidant,
In addition to the metal carboxylate, various additives such as an antistatic agent, a lubricant, an ultraviolet absorber, and a pigment can be added.

A die is selected depending on the application in which these compositions are melt-extruded by a kneading extruder and molded. The melt extrusion temperature varies depending on the polyethylene resin used, and an optimum temperature is selected.

Examples The present invention will be described in detail with reference to examples.

Examples 1 to 22 100 parts by weight of low-density polyethylene "Showrex L-133K" manufactured by Showa Denko KK, and rutile-type titanium dioxide powder "Super Titania G" manufactured by Showa Titanium Co., Ltd. (average particle size: 0.2 [mu] m). Phenolic antioxidants,
A phosphorus-based antioxidant and a metal carboxylate were dry-mixed with a Henschel mixer (manufactured by Mitsui Miike Co., Ltd.) at the ratios shown in Table 1 to prepare a polyethylene resin composition. The mixing time was 5 minutes.

Next, the mixture was kneaded at 110 to 120 ° C. for 5 minutes by a kneader, and was melt-extruded at 70 rpm by a extruder at a die temperature of 180 ° C. to obtain cylindrical pellets having a diameter of 3 mm and a length of 3 mm.

Using these pellets, injection molding was performed at a molding temperature of 150 ° C. to prepare plates of 90 × 50 × 2 mm.

To test the heat resistance of these plates, they were heat-degraded in a forced hot air circulating electric dryer at 125 ° C for 48 hours or 96 hours as shown in Table 1, and the yellow index (YI) of these plates was determined. It was measured. For this YI measurement, Tokyo Denshoku Co., Ltd. measuring machine Color Ace TC-8600 was used. Table 1
Has a difference ΔI between the measured value YI value and the YI value of the standard white plate.
Displayed in YI. The greater the value of ΔYI, the greater the degree of yellowing, indicating poor heat resistance.

In addition, among the phenolic antioxidants in Table I, A is 3,9-bis [2- [3- (3-t-butyl-4-).
(Hydroxy-5-methylphenyl) -propionyloxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane B is 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate C is triethylene glycol-bis [3- (3-t-
Butyl-5-methyl-4-hydroxyphenyl) propionate] And among the phosphorus antioxidants in Table I, b is tetrakis (2,4-di-t-butylphenyl) 4,
4'-biphenylene phosphite C is tris (2,4-di-t-butylphenyl) phosphite It is.

Comparative Examples 1 to 6 100 parts by weight of the same low-density polyethylene as in Examples 1 to 22,
As shown in Table 2, with respect to 100 parts by weight of the same titanium dioxide powder as in Examples 1 to 22, a polyethylene resin composition containing no phenolic antioxidant, phosphorus-based antioxidant, or metal carboxylate was added. I made things. The manufacturing method, pelletization, plate forming, and the evaluation method are described in Example 1.
This is the same condition as 2222. The symbols used for the phenolic and phosphorus antioxidants in Table 2 are also the same as in Table 1.

From these results, it can be seen that when any of them is not added, the heat resistance is inferior.

In addition, when no fatty acid metal salt is added, the die lip is stained during injection molding, and 40 μm is added.
In the case of a film of about m, many microgrids were clearly observed and kneading was insufficient.

Effects of the Invention According to the present invention, a phenol-based and phosphorus-based antioxidant, and a metal carboxylate are added to a titanium oxide-containing polyethylene resin, whereby the heat resistance is further improved,
A thermoplastic resin composition having improved kneading workability is obtained.

────────────────────────────────────────────────── (5) Continuation of the front page (51) Int.Cl. ⁶ identification symbol FI C08K 5: 135: 49) (56) References JP-A-59-41343 (JP, A) JP-A-64-36633 (JP) JP-A-2-99541 (JP, A) JP-A-57-202346 (JP, A) JP-A-57-200455 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB Name) C08K 3/00-13/08

Claims (1)

(57) [Claims] 1. The content of titanium oxide is 5 to 250 parts by weight, the phenolic antioxidant is 0.001 to 0.5 parts by weight, and the phosphorus antioxidant is 0.1 to 100 parts by weight of polyethylene resin.
A thermoplastic resin composition having excellent whiteness, comprising 001 to 1 part by weight and metal carboxylate at 1.0 to 10 parts by weight.