JPS6153384B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a titanium oxide-containing thermoplastic resin composition having anti-yellowing performance and economic thermal stability. Thermoplastic resins are used in everything from industrial parts to household items.
Although it is used in a wide range of fields, it is colored in various colors for aesthetic reasons, light-shielding properties, and reflective properties. At this time, titanium oxide is often used as the pigment. Particularly in fields such as meter boxes and lamp housings where high reflectance (whiteness) and light-shielding properties are required at the same time, it is necessary to add a large amount of titanium oxide. In addition, various phenolic antioxidants are generally added to thermoplastic resins in order to maintain thermal stability within the forming machine and thermal stability over time.
However, when titanium oxide and a phenolic antioxidant are used together, the phenolic antioxidant is oxidized to a quinone-type compound, which takes on a yellow color, although it is not clear what effect the titanium oxide has. For this reason, thermoplastic resins colored white using titanium oxide should not be left for long periods of time, exposed to high temperatures, or exposed to sunlight, fluorescent lights, incandescent lamps, or other environments with a lot of light or ultraviolet rays. In an environment where both are present at the same time, there is a drawback that the color changes to yellow. Generally, as the amount of titanium oxide added or the amount of phenolic antioxidant added increases, the degree of yellowing increases. Therefore, in thermoplastic resin compositions containing titanium oxide, it has been desired to improve not only thermal stability but also anti-yellowing properties. In view of the above-mentioned problems, the present inventors have conducted extensive research and found that thermoplastic resins containing titanium oxide have the following properties:
It has been discovered that by adding a phosphoric acid antioxidant among various antioxidants, a thermoplastic resin composition that is free from yellowing and has good thermal stability in a molding machine can be obtained, Already suggested. Furthermore, as a result of repeated research in order to fully satisfy the thermal stability within the molding machine and of molded products over time, we have identified phenolic antioxidants or thioether antioxidants for such titanium oxide-containing thermoplastic resins. By using these together, the intended purpose was achieved and the present invention was completed. That is, the present invention uses 0.1 to 250 parts by weight of titanium oxide, 0.01 to 2.0 parts by weight of a phosphorus antioxidant, and a phenol having a substituent having 4 or more carbon atoms at the para position to 100 parts by weight of a thermoplastic resin. The present invention is a thermoplastic resin composition containing 0.005 to 1.0 parts by weight of a antioxidant or (and) 0.01 to 2.0 parts by weight of a thioether antioxidant. Thermoplastic resins used in the present invention include polyolefins such as polyethylene, polypropylene, and polybutene; styrenic polymers such as polystyrene, AS, and ABS; nylon 6, nylon 6, etc.
Examples include homopolymers or copolymers such as polyamides such as No. 6, polyvinyl chloride, and the like alone or in mixtures, and polyolefins containing polypropylene as a main component are particularly preferably used. The titanium oxide is not particularly limited, and any commercially available titanium oxide may be used. The amount of titanium oxide blended is 0.1 to 250 parts by weight per 100 parts by weight of the thermoplastic resin, and preferably 0.1 to 1.0 parts by weight as a pigment.
The amount is 1.0 to 250 parts by weight, preferably 4.0 to 250 parts by weight when whiteness and light-shielding properties are required at the same time for lamp housings, meter boxes, etc. If the amount of titanium oxide is less than the lower limit, sufficient whiteness and light-shielding properties cannot be obtained.
Furthermore, if the amount of titanium oxide is more than the above upper limit, kneading and pelletizing using an extruder becomes difficult when producing a thermoplastic resin molded article, which is not industrially suitable. The combined use of a phosphorus-based antioxidant in the thermoplastic resin containing titanium oxide of the present invention not only improves the thermal stability of the thermoplastic resin in the molding machine, but also improves the phenolic antioxidant described below. Demonstrates the effect of suppressing yellowing effect.
As phosphorus antioxidants, aliphatic or aromatic phosphite esters are generally used, such as However, it is expressed by the formula 1≦n, n'≦50, 1≦m, m'≦20, but especially 10≦n, n'≦25, 1≦
m, m′≦3 is preferably used. Also, However, although it is expressed by the formula 1≦2≦5, one in which n=2 is particularly preferably used. Also However, 1≦n, n', n'', n≦5, 1≦m≦5, and those in which n=m=2 are particularly preferably used. Phosphorous antioxidants such as those mentioned above. The blending amount of the phosphorus antioxidant is generally 0.01 to 2.0 parts by weight and preferably 0.03 to 2.0 parts by weight per 100 parts by weight of the thermoplastic resin.If the blending amount of the phosphorus antioxidant is lower than the above lower limit, Sufficient thermal stability cannot be obtained, and even if the temperature is higher than the above upper limit, the thermal stability will not be improved and the price will only increase unnecessarily.In the thermoplastic resin composition containing titanium oxide of the present invention, It is extremely important to use a phenolic antioxidant or a thioether antioxidant having a substituent with 4 or more carbon atoms in the para-position together with a phosphorus antioxidant in order to obtain thermal stability over time. As mentioned above, various phenolic antioxidants are generally added and used in order to maintain the thermal stability of thermoplastic resins.However, in thermoplastic resins containing titanium oxide, phenolic antioxidants are used. When an inhibitor is added, yellowing occurs.However, in the present invention, a specific phenolic antioxidant having a substituent having 4 or more carbon atoms at the para position is selected. , by using it in combination with a phosphorus-based antioxidant, the thermoplastic resin composition containing titanium oxide does not yellow.
This provides thermal stability over time. That is, as shown in the comparative example below, 2,6-di-t-butyl-4-methylphenol was used as a phenolic antioxidant. When used, thermal stability over time is not exhibited and yellowing is observed significantly. On the other hand, when various phenolic antioxidants as shown in the examples are used, it is clear that economical thermal stability is exhibited without yellowing. From these results, it is necessary for the phenolic antioxidant used in the present invention to have a substituent at the para position having a large number of carbon atoms, and it is generally preferable that the substituent has 4 or more carbon atoms. The phenolic antioxidant having a substituent having 4 or more carbon atoms at the para-position is not particularly limited, and commonly commercially available ones can be used. Examples include the following: In the present invention, the amount of the phenolic antioxidant having a substituent having 4 or more carbon atoms at the para position is generally based on 100 parts by weight of the thermoplastic resin.
The amount is 0.005 to 1.0 parts by weight, preferably 0.01 to 0.5 parts by weight; if it is lower than the above lower limit, sufficient thermal stability over time of the molded product cannot be obtained, and if it is higher than the above upper limit, There is little improvement in thermal stability over time, and not only does it become unnecessarily expensive, but it also causes a small amount of yellowing, which is undesirable. Furthermore, in the present invention, similar effects can be obtained by using a thioether antioxidant instead of or in combination with the phenolic antioxidant having a substituent having 4 or more carbon atoms at the para position. .
The thioether antioxidant is not particularly limited to known ones, and commonly commercially available ones can be used. for example However, 1≦m≦5, 1≦m′≦5, 5≦n≦30,
It is expressed by the formula 5≦n′≦30, but especially 1
≦m≦3, 1≦m′≦3, 10≦n≦20, 10≦m′≦
20 is preferably used. Specifically, dilauroyl-thio-propionate, dimyristyl-thio-propionate, distearyl-thio-
Commonly used such as propionate. The amount of the thioether antioxidant in the present invention is 0.01 to 2.0 parts by weight, preferably 0.05 to 2.0 parts by weight, per 100 parts by weight. If the amount of the thioether antioxidant is lower than the above lower limit, sufficient thermal stability over time of the formed product cannot be obtained. Moreover, even if it is higher than the above-mentioned upper limit, there is little improvement in thermal stability over time and it becomes undesirably expensive. In the present invention, the order in which the thermoplastic resin, titanium oxide, phosphorus antioxidant, phenolic antioxidant having a substituent having 4 or more carbon atoms at the para position, and thioether antioxidant are mixed is not particularly limited. First, each component may be mixed at the same time, or several components may be mixed in advance and the remaining components may be mixed later. Further, the mixing method is not particularly limited, and is generally carried out using a tumbler type blender, a V-type blender, a Henschel mixer, a ribbon mixer, or the like. Furthermore, it is also possible to adopt a method of changing the mixing order and equipment, such as mixing several types in advance in a Henschel mixer, then adding the rest and mixing in a tumbler type blender. In addition to the above-mentioned components, the thermoplastic resin composition of the present invention also contains conventionally known ultraviolet absorbers, lubricants, antistatic agents, nucleating agents, pigments, glasses such as glass fibers and glass beads, and charcoal. , talc, barium sulfate, mica, asbestos, silica, magnesium hydroxide, basic magnesium carbonate, aluminum hydroxide, kaolin, and other inorganic fillers may be added. In particular, the combined use of the above-mentioned glasses and inorganic fillers is suitable for thermoplastic compositions containing the titanium oxide of the present invention that require high light shielding and high reflectance. EXAMPLES In order to explain the present invention more specifically, Examples and Comparative Examples will be given below, but the present invention is not limited to these Examples. The phosphorus antioxidants used in Examples and Comparative Examples are as follows, and are abbreviated as phosphorus A, phosphorus B, and phosphorus C, respectively. In addition, for the yellowing test shown in Examples and Comparative Examples, a plate-shaped test piece of 78 mm x 48 mm x 3.5 mm was prepared using an injection molding machine, and this was placed in a sunshine weather meter manufactured by Suga Co., Ltd. This was observed after 120 hours. As a result, those with no visible yellowing are ◎, those with very slight yellowing but no problem for practical use are 0, those with a little yellowing are △, and those with severe yellowing are × In addition, in the tests of thermal stability over time shown in Examples and Comparative Examples, a 100 mm x 50
A sheet of mm x 0.5 mm was placed in a hot air circulating biaxial rotary gear oven manufactured by Suga Corporation and set at 145°C, and the time required for 1/3 of the sheet to deteriorate and disappear was measured. Example 1 (and Comparative Example 1) Titanium oxide (manufactured by LaPorte, Teona) in the proportion shown in Table 1 was added to 100 parts by weight of polypropylene (ME140, MI9 homopolymer manufactured by Tokuyama Soda).
113), various antioxidants, and calcium stearate were mixed using a super mixer (manufactured by Kawada Seisakusho). Note that calcium stearate was added to the total composition in a common amount of 0.1% for each sample. Next, the mixture was melt mixed using an extruder with a kneader (resin temperature 260°C) and pelletized. This sample was subjected to a yellowing test, a melt index measurement and a thermal stability test over time, and the results are also listed in Table 1.

【table】

[Table] Example 2 (and Comparative Example 2) Polypropylene (MS640, MI6 manufactured by Tokuyama Soda Co., Ltd.)
5 block copolymer with polyethylene) 100
Various titanium oxides, various antioxidants, and calcium stearate were mixed in the same manner as in Example 1 in the proportions shown in Table 2 based on the weight part, and after pelletizing, yellowing test and melt index measurement and heating over time were performed. A stability test was conducted and the results are also listed in Table 2.

[Table] Example 3 (and Comparative Example 3) Various inorganic fillers in the proportions shown in Table 3 based on 100 parts by weight of polypropylene (random copolymer with polyethylene of ME30 and MI4 manufactured by Tokuyama Soda Co., Ltd.),
Titanium oxide, various antioxidants, and calcium stearate were mixed and pelletized in the same manner as in Example 1, and then a yellowing test, melt index measurement, and thermal stability test over time were conducted, and the results are also listed in Table 3. did.

【table】

【table】

Claims (1)

[Claims] 1 Titanium oxide based on 100 parts by weight of thermoplastic resin
0.1 to 250 parts by weight, 0.01 to 2.0 parts by weight of a phosphorous antioxidant, and 0.005 to 1.0 parts by weight of a phenolic antioxidant having a substituent with 4 or more carbon atoms at the para position, or (and) thioether oxidation. inhibitor
A thermoplastic resin composition containing 0.01 to 2.0 parts by weight. 2. The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin is a polyolefin. 3. The thermoplastic resin composition according to claim 2, wherein the polyolefin is polypropylene. 4. The thermoplastic resin composition according to claim 1, wherein the phosphorus antioxidant is an aliphatic or aromatic phosphite.