JPH0544105Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic material storage container. More specifically, the present invention relates to a magnetic material storage container such as an audio cassette half, an audio cassette P case, a CD case, etc., which has excellent heat resistance and is suitable for being left in a car or used outdoors. [Prior Art] Conventionally, audio cassettes, which are acoustic software components, have been mainly used outdoors, but in recent years,
With the spread of in-vehicle audio, outdoor use and leaving it in cars are becoming more common year by year. Audio cassettes used in such applications are required to have good transparency as well as excellent heat resistance. By the way, polystyrene has conventionally been used as the main material for audio cassettes, but its heat resistance is not always fully satisfactory, and audio cassettes made of polystyrene are used, for example, in automobiles with high outside temperatures during the summer. If you leave it in the car, it will easily become deformed.
The problem often arises that tape running becomes impossible. [Problems to be solved by the invention] The present invention solves the problems of conventional magnetic material storage containers such as audio cassettes, and provides a magnetic material storage container with excellent transparency and good heat resistance. It was made with the purpose of providing. [Means for Solving the Problems] As a result of extensive research in order to develop a magnetic material storage container having the above-mentioned favorable properties, the present inventors developed a copolymer of a specific styrene and maleic anhydride. discovered that a resin composition obtained by injection molding containing higher saturated monovalent fatty acids in a predetermined ratio could be suitable for the purpose, and based on this knowledge, completed the present invention. It came to this. That is, in the present invention, (a) the weight average molecular weight is 25×
10 ⁴ or more and the content of maleic anhydride units is 2
It is a copolymer of ~25% by weight of styrene and maleic anhydride, and the number of peaks in the maleic anhydride composition distribution curve by gradient liquid chromatography is 2 or 3, and the maleic anhydride content of each peak is A magnetic material storage container made by injection molding a resin composition containing a copolymer with a difference within 4% by weight and (b) a higher saturated monovalent fatty acid of 0.05% by weight or more based on the weight of the resin composition. It provides: The present invention will be explained in detail below. In the resin composition that is the material of the magnetic material storage container of the present invention, a copolymer of styrene and maleic anhydride is used as component (a). The styrene component in this copolymer may be not only styrene but also styrene derivatives such as α-methylstyrene, dichlorostyrene, and dimethylstyrene, or a portion of the styrene may be methacrylic acid, methyl methacrylate, It may be substituted with a copolymerizable monomer such as methyl acrylate, ethyl methacrylate, acrylonitrile, methacrylonitrile, or a halogen-containing vinyl monomer. On the other hand, the maleic anhydride component is not limited to maleic anhydride, but may be partially substituted with itaconic anhydride, ethylmaleic anhydride, chloromaleic anhydride, or the like. When copolymerizing the above-mentioned styrene and maleic anhydride, solution polymerization method, bulk polymerization method, bulk polymerization method, etc.
Any method can be selected from known polymerization methods such as suspension polymerization. The content of maleic anhydride units in this copolymer must be in the range of 2 to 25% by weight, preferably 4 to 20% by weight. This content is 2% by weight
If it is less than 25% by weight, the resulting storage container may have insufficient heat resistance, and if it exceeds 25% by weight, the mechanical properties of the container tend to deteriorate. In addition, the copolymer has a weight average molecular weight of 25×10 ⁴
Must be above 260,000 yen, preferably 260,000 yen or more
400,000. If the weight average molecular weight is less than 25×10 ⁴ , the mechanical strength of the resin composition may be low, making it unsuitable for injection molding. moreover,
It is important that the maleic anhydride composition distribution curve determined by gradient liquid chromatography has two or three peaks, and that the difference in maleic anhydride content between the peaks is within 4% by weight. Gradient liquid chromatography is a method in which various solids or liquids are used as a fixed layer, and a sample mixture placed at one end of the layer is moved using an appropriate developer, and the difference in movement speed is determined based on the adsorption properties and distribution coefficients of each component. It is a type of so-called chromatography, which is a technology that uses chromatography to separate these substances from each other. The characteristics of the gradient liquid chromatography method are that two types of solvents with different solubility powers are used as developing agents, and only the solvent with the lower solubility power is first passed through the column, and then the solvent with the higher solubility power is passed through the column. The method is to gradually and continuously increase the mixing rate of a solvent with a high solvent power. A copolymer of styrene and maleic anhydride has a property that the larger the content of maleic anhydride units, the more soluble it is in a solvent with a higher dissolving power. Therefore, by analyzing mixtures of styrene-maleic anhydride copolymers with different contents of maleic anhydride units using a gradient liquid chromatography method, the maleic anhydride composition in the copolymer mixture can be determined. rate distribution can be obtained. When a copolymer of styrene and maleic anhydride is produced by a multi-stage polymerization method, a mixture of styrene-maleic anhydride copolymers having a plurality of maleic anhydride composition ratios depending on the number of polymerization stages is obtained. For example, if the copolymer is produced by a two-stage polymerization method, a mixture of two types of copolymers having two maleic anhydride composition ratios will be obtained. When the resulting mixture is analyzed using the gradient liquid chromatography method described above, a composition ratio distribution curve of maleic anhydride having two peaks, for example, is obtained. Therefore, in this specification, for example, 2
The styrene-maleic anhydride copolymer (mixture) produced by step polymerization can be referred to as "styrene-maleic anhydride copolymer whose maleic anhydride composition distribution curve has two peaks." The copolymer according to the present invention can be produced by a solution polymerization method, a bulk polymerization method, a suspension polymerization method, etc., but a bulk multistage polymerization method is particularly suitable. lumpy 2
In the step polymerization method, styrene and maleic anhydride are supplied to a first polymerization vessel to perform a copolymerization reaction, and the resulting reaction product is transferred to a second polymerization vessel, and maleic anhydride is also supplied to the second polymerization vessel. The polymerization conditions of the first polymerization vessel and the second polymerization vessel to perform the copolymerization reaction are as follows:
The maleic anhydride composition distribution curve is adjusted as appropriate so that it becomes the specific curve described above. The copolymer according to the present invention can be produced by multi-stage polymerization as described above, but commercially available Moamax UG281 or UG461 (Idemitsu Petrochemical Co., Ltd.)
(manufactured by) can also be used. In the resin composition according to the present invention, the higher saturated monovalent fatty acid used as component (b) preferably has 10 to 24 carbon atoms, particularly preferably a straight chain fatty acid with 14 to 22 carbon atoms. Specific examples include lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid. These may be blended alone or in combination of two or more. The blending amount needs to be 0.05% by weight or more based on the total weight of the resin composition. If this amount is less than 0.05% by weight, the effect of improving mold releasability is insufficient. In addition, if the blending amount is too large, mechanical strength and heat resistance may decrease, or there is a risk of bleeding, which may adhere to the molded product during continuous molding, resulting in a defective product. Therefore, preferably 0.05 to 1.0% by weight,
More preferably, it is selected in the range of 0.1 to 0.8% by weight. The resin composition can be prepared, for example, by adding the higher saturated monovalent fatty acid before or during the polymerization of styrene and maleic anhydride and directly polymerizing it, or by adding a copolymer of styrene and maleic anhydride. This can be carried out by mechanically mixing the fatty acid into beads or pellets and then melt-kneading the mixture. Furthermore, the resin composition may include thermoplastic resins such as polystyrene, polyolefin, polyester, polybutadiene, SBS,
Rubbers such as MBS and MAS, antioxidants, flame retardants,
Various additives such as ultraviolet absorbers, lubricants, and colorants can be added. The magnetic material storage container of the present invention can be manufactured by injection molding the thus prepared resin composition into a desired shape. [Effects of the invention] The magnetic material storage container of the invention is obtained by injection molding a resin composition comprising a copolymer of specific styrene and maleic anhydride mixed with a required amount of higher saturated monovalent fatty acids. It is transparent and has excellent heat resistance of over 100℃, so it will not deform in any way even if it is left in a car when the outside temperature is high in the summer, and it is also suitable for outdoor transportation and use. The product value is high, and demand is expected to increase. The magnetic material storage container of the present invention can be applied to, for example, an audio cassette half, an audio cassette P case, a CD case, etc. [Example] Next, the present invention will be explained in more detail with reference to Examples. (Example 1) A copolymer of styrene and maleic anhydride with a weight average molecular weight of 30×10 ⁴ and a content of maleic anhydride units of 8 to 8.5% by weight, and maleic anhydride was determined by gradient liquid chromatography. A copolymer whose acid composition distribution curve had two peaks and whose maleic anhydride content differed within 4% by weight was produced by a bulk two-stage polymerization method. The proportion of the obtained copolymer and the total amount of the composition is
0.1% by weight of beef tallow stearic acid [Nippon Yuushi Co., Ltd.]
After preparing a resin composition containing beef tallow stearic acid, 64% by weight of stearic acid, and 30% by weight of palmitic acid (manufactured by Sakura), it was injection molded under the following conditions to produce audio cassette half A and audio cassette. P case B was produced. Molding conditions Injection molding machine Clamping force 100-150 TON Mold A: 2 pairs of cassette halves B: 4 cassette P cases (lid, main body) Molding temperature 220-250℃, mold temperature 50-75℃ Molding cycle 12 ~15 seconds The heat distortion temperature of this resin composition was 107°C. Next, tape and other necessary parts are assembled into the cassette half A obtained in this way to make a finished product capable of recording and playback.Then, with this half inserted into the audio cassette P case B, the temperature inside the car is adjusted. After leaving the tape in an oven at 80°C, 90°C, and 100°C for 4 hours, we observed changes in the product and confirmed whether the tape could be played. The results are shown in Table 1. As can be seen from this table, there was no deformation at all and tape playback was good. (Example 2) A copolymer of styrene and maleic anhydride with a weight average molecular weight of 30×10 ⁴ and a content of maleic anhydride units of 8 to 8.5% by weight, and maleic anhydride was determined by gradient liquid chromatography. A copolymer in which the number of peaks in the acid composition distribution curve was 3 and the difference in maleic anhydride content between the peaks was within 4% by weight was produced by a bulk two-stage polymerization method. The proportion of the obtained copolymer and the total amount of the composition is
0.1% by weight of beef tallow stearic acid [Nippon Yushi Co., Ltd.]
A resin composition containing beef tallow stearic acid, 64% by weight of stearic acid, and 30% by weight of palmitic acid (manufactured by Sakura Co., Ltd.) was prepared, and the following procedure was repeated in the same manner as in Example 1 to prepare an audio cassette half and an audio cassette P. A case was made and evaluated. The results are shown in Table 1. As can be seen from this table, there was no deformation at all and tape playback was good. (Comparative Example 1) Instead of the resin composition in Example 1, GP-
The same procedure as in Example 1 was conducted except that PS (Idemitsu Styrene US305, manufactured by Idemitsu Petrochemical) was used. The results are shown in Table 1. Note that the heat distortion temperature of GP-PS was 88°C. As can be seen from this table, deformation occurred at temperatures above 90°C, and tape playback was poor. (Comparative Example 2) A copolymer of styrene and maleic anhydride with a weight average molecular weight of 30×10 ⁴ and a content of maleic anhydride units of 8 to 8.5% by weight. A copolymer whose acid composition distribution curve had a peak number of 1 was produced by a bulk one-stage polymerization method. The obtained copolymer and beef tallow stearic acid having a proportion of 0.1% by weight based on the total amount of the composition [manufactured by Nihon Yuushi Co., Ltd., trade name (Sakura)] beef tallow stearic acid, stearic acid 64% by weight,
A resin composition containing 30% by weight of palmitic acid was prepared, and an audio cassette half and an audio cassette P case were produced and evaluated in the same manner as in Example 1. The results are shown in Table 1. As can be seen from this table, deformation occurred at temperatures above 90°C, and tape playback was also poor. (Comparative Example 3) A copolymer of styrene and maleic anhydride with a weight average molecular weight of 30×10 ⁴ and a content of maleic anhydride units of 8 to 8.5% by weight. A copolymer with an acid composition distribution curve having two peaks and a difference in maleic anhydride content of each peak of more than 4% by weight was produced by a bulk two-stage polymerization method. The ratio of the obtained copolymer to the total amount of the composition is
0.1% by weight of beef tallow stearic acid [Nippon Yushi Co., Ltd.]
A resin composition containing beef tallow stearic acid, 64% by weight of stearic acid, and 30% by weight of palmitic acid (manufactured by Sakura Co., Ltd.) was prepared, and the following procedure was repeated in the same manner as in Example 1 to prepare an audio cassette half and an audio cassette P. A case was made and evaluated. The results are shown in Table 1. As can be seen from this table, deformation occurred at temperatures above 90°C, and tape playback was also poor. (Comparative Example 4) A copolymer of styrene and maleic anhydride with a weight average molecular weight of 30×10 ⁴ and a content of maleic anhydride units of 8 to 8.5% by weight, and maleic anhydride obtained by gradient liquid chromatography. A copolymer in which the number of peaks in the acid composition distribution curve was 4 and the difference in maleic anhydride content between the peaks was within 4% by weight was produced by a bulk two-stage polymerization method. The ratio of the obtained copolymer to the total amount of the composition is
0.1% by weight of beef tallow stearic acid [Nippon Yushi Co., Ltd.]
A resin composition containing beef tallow stearic acid, 64% by weight of stearic acid, and 30% by weight of palmitic acid (manufactured by Sakura Co., Ltd.) was prepared, and the following procedure was repeated in the same manner as in Example 1 to prepare an audio cassette half and an audio cassette P. A case was made and evaluated. The results are shown in Table 1. As can be seen from this table, deformation occurred at temperatures above 90°C, and tape playback was also poor. 【table】

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a cassette half which is an example of an embodiment of the present invention, and FIG. 2 is a perspective view of an audio cassette P case which is also another embodiment.

Claims (1)

[Scope of Claim for Utility Model Registration] (a) A copolymer of styrene and maleic anhydride with a weight average molecular weight of 25×10 ⁴ or more and a content of maleic anhydride units of 2 to 25% by weight; A copolymer in which the number of peaks in the maleic anhydride composition distribution curve determined by gradient liquid chromatography is 2 or 3, and the difference in maleic anhydride content between the peaks is within 4% by weight, and (b) a resin composition. A magnetic material storage container made by injection molding a resin composition containing 0.05% by weight or more of higher saturated monovalent fatty acids based on the weight of the object.