JPS63119084A - Cassette half - Google Patents

Abstract

PURPOSE:To satisfy high performance and high quality such as reproducing performance for sound or the like, environmental-resistance and sense of depth by forming the titled cassette halves by a polypropylene resin component where the volume percentage of an inorganic reinforcement agent occupied in the component is <=50vol% and the specific gravity of the compound is >=1.8. CONSTITUTION:The titled cassette halves are formed by employing the polypropylene resin component where the volume percentage of the inorganic reinforcement agent is below 50vol% and the specific gravity of the compound is over 1.8. When the volume percentage of the inorganic reinforcement agent occupied in the compound exceeds 50vol%, the forming processing performance of the compound is deteriorated and the forming by injection molding or the like is made difficult. Moreover, if the specific gravity of the compound is less than 1.8, no high function nor high quality is attained. Furthermore, zinc oxide is used as the inorganic reinforcement agent in the compound and the weight percentage of the zinc oxide is preferably to be shared by 20wt% or over.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to the provision of cassette halves for audio cassette tapes, video cassette tapes, etc.

(Prior art and its problems) Conventionally, polystyrene resin has been mainly used as a base material for cassette halves constituting audio cassette tapes, video cassette tapes, etc. However, there is a strong demand for high functionality and high quality tapes, such as sound reproduction performance, environmental resistance, and a solid feel. There is a limit to the ability of half-metal materials to meet these requirements, so metallic materials such as aluminum die-casting and composite polypropylene resins filled with inorganic fillers such as calcium carbonate as disclosed in JP-A No. 58-133676 have been applied as improved base materials. There is. However, although cassette halves made of metal materials satisfy requirements such as playability, environmental resistance, and solid feel, they are somewhat inferior in resonance properties and have problems with the ease of molding cassette halves, and conventional composite polypropylene The cassette half, which is made of resin as a base material, is intended to improve environmental resistance, and although it improves some of the playability of sounds and the sense of solidity, it is still insufficient.

The present inventors have an object to provide a high-performance, high-quality cassette half that is superior to the conventionally used cassette halves based on polystyrene resins or composite polypropylene resins, and can replace cassette halves made of metal materials. As a result of various studies, we have completed the cassette half of the present invention, which satisfies high functionality such as sound reproduction performance, environmental resistance, solid feel, and high quality.

(Means for solving the problem) The present invention provides: (1) A polypropylene resin composition in which the volume fraction of an inorganic reinforcing agent in the composition is 50% by volume or less, and the specific gravity of the composition is 1.8 or more. or (2) 20% of the inorganic reinforcing agent as the inorganic reinforcing agent in the composition.
! The above (1) characterized in that not less than % of zinc oxide is
A cassette half formed from the polypropylene resin composition described in item 2 is provided.

The polypropylene resin composition referred to in the present invention is a polypropylene resin filled with an inorganic reinforcing agent to strengthen it.

In the present invention, the polypropylene resin is a propylene homopolymer or a copolymer of propylene and an α-olefin such as ethylene or butene 1, and each may be used alone or in combination.

Inorganic reinforcing agents include 1, such as calcium carbonate, talc, barium sulfate, clay, silica, mica, titanium oxide, iron oxide, titanium oxide, copper, lead, etc., steel, brass, AI,
It is an artificial or natural inorganic reinforcing agent in the form of fine powder or fibers such as glass. These inorganic reinforcing agents can be coupled with the polypropylene resin by a known method, or can be treated with a known treatment method to improve the affinity, such as silane coupling agents, titanium camplating agents, higher fatty acids, fatty acid metal salts, fatty acids and It may be used after surface treatment with a treatment agent such as organic acid ester and amide, organic acid, resin acid, etc.
Known auxiliary agents may be used in combination to enhance camplining or affinity.

The cassette half of the present invention has an inorganic reinforcing agent volume fraction of 50
It is formed by using a polypropylene resin composition having a specific gravity of 1.8 or more and a specific gravity of 1.8 or more. Therefore,
The above-mentioned inorganic reinforcing agents may be used alone or in combination as long as the conditions of the present invention are satisfied.

The volume fraction of the inorganic reinforcing agent in the composition must be 50% by volume or less. When the volume fraction exceeds 50% by volume, the moldability of the composition decreases, making it difficult to mold the cassette half of the present invention by injection molding or the like.

Further, the specific gravity of the composition needs to be 1.8 or more, preferably 2.0 or more. If the specific gravity is less than 1.8, the high functionality and high quality aimed at by the cassette half of the present invention cannot be achieved.

Further, in the cassette half of the present invention, it is preferable that zinc oxide is used as an inorganic reinforcing agent component in the composition, and the weight percentage of zinc oxide in the inorganic reinforcing agent is 20% by weight or more.

When the weight percentage of zinc oxide in the inorganic reinforcing agent is 20 weight percent or more, it is possible to more easily obtain a cassette half having high functionality and high quality, which is the object of the present invention.

(Effects of the Invention) An object of the present invention is to easily provide a high-performance, high-quality cassette half.

The features of the cassette half of the present invention are as follows.

(11) Since the polypropylene resin composition can be molded by a known molding method such as injection molding, it can be provided more easily than metal materials such as aluminum die-cast cassette halves.

(2) Because it is made of a polypropylene resin composition with a specific gravity of 1.8 or more, it has a heavier feel than conventional cassette halves made of polypropylene fruit tree compositions or polypropylene resin compositions, and is made of metal materials such as aluminum die. It is a high quality cassette half comparable to the cast cassette half.

(3) Polypropylene resin is used as the base material and the specific gravity is 1.
．． Since it is large (8 or more), internal loss is large and resonance occurs (
Because it is small and less susceptible to the effects of external vibrations, etc., it has superior sound reproduction properties when used as a cassette tape, compared to cassette halves made of conventional polypropylene resin compositions or composite polypropylene resin compositions.

(4) It has superior heat resistance and other properties compared to conventional polypropylene resins, so it has excellent environmental resistance and is highly functional as cassette tapes that may be exposed to high temperatures, such as car audio and outdoor audio.

As described above, the cassette half of the present invention has higher functionality and superior quality than conventional cassette halves made of polystyrene resins, composite polypropylene resin compositions, etc., and is easier to mold than metal materials, so it can be used industrially. It becomes possible to provide extremely high quality audio or video cassette tapes.

The present invention will be explained below with reference to Examples.

(Example) Example 1 75 parts by weight of zinc oxide (zinc white average particle size 0.5μ Sakai Chemical Industry @) was added to 25 parts by weight of polypropylene resin (propylene-ethylene block copolymer with MFI of 4 at 230°C) at 210°C. The mixture was filled and blended using a kneader to create composition pellets. This composition pellet was injection molded (molding temperature 2
10°C), and an audio cassette half and a dumbbell-shaped test piece were prepared.

The following items were tested on the prepared cassette half and test piece.

Environmental resistance (1) After assembling a pair of two cassette halves at one point, the screw fixing part in the center, with a torque strength of 1 kg,
The cassette was left in an environment of 90° C. for 48 hours, and the clearance distance between the cassette halves was measured.

Environmental resistance (2): A piece of the cassette half was left in a 90°C environment for 48 hours, and the average shrinkage rate was determined from the shrinkage rates of the long sides and short pieces of the cassette half.

Resonance sharpness (Q value): A dumbbell-shaped test piece was subjected to non-contact forced vibration at the excitation frequency from an oscillator, and the resonance sharpness (Q value) was determined from the resonance frequency.

Sound reproducibility: A cassette tape was assembled from a pair of cassette halves using a standard tape on which standard audio was recorded.

Add this standard audio recording cassette tape to the audio deck (
IsoAD-FF60) was used to reproduce the sound in a listening room, and the reproducibility of the sound was determined.

The above test results are shown in Table 1.

Example 2 A composition was obtained in the same manner as in Example 1 from 30 parts by weight of polypropylene resin, 50 parts by weight of zinc oxide, and 20 parts by weight of acrylic acid surface-treated calcium carbonate (average particle size 3 μm), The test was conducted in the same manner as in Example 1. The results are shown in Table 1.

Example 3 A composition was prepared in the same manner as in Example 1 from 30 parts by weight of polypropylene resin, 15 parts by weight of zinc oxide, and 55 parts by weight of barium sulfate (average particle size 4.5μ Sakai Kagaku Kogyo n). was obtained and tested in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 A composition was obtained in the same manner as in Example 1 from 50 parts by weight of polypropylene resin and 50 parts by weight of calcium carbonate surface-treated with acrylic acid, and tested in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 Polystyrene (Asahi Kasei Corporation Styron H-8180:
MIPS), an audio cassette half and a dumbbell-shaped test piece were prepared in the same manner as in Example 1, and tested in the same manner as in Example 1. The results are shown in Table 1.

(Margin below)

Claims (2)

[Claims] (1) A cassette half formed of a polypropylene resin composition in which the volume fraction of the inorganic reinforcing agent in the composition is 50% by volume or less and the specific gravity of the composition is 1.8 or more. (2) As an inorganic reinforcing agent in the composition, 20% of the inorganic reinforcing agent
A cassette half formed from the polypropylene resin composition according to claim 1, wherein at least % by weight is zinc oxide.