JP4694718B2 - Elastomer composition and cabinet - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an elastomer composition and a cabinet using the elastomer composition.
[0002]
[Prior art]
For example, the hard disk cabinet (1) shown in FIG. 1 is composed of a pair of boxes (2, 3) joined by hinges (8), and the main body of the box (2, 3). (4,5) is made of hard thermoplastic resin such as polypropylene, and the corners (6,7) are made of elastomer to prevent damage due to stress concentration. As the elastomer, for example, a composition obtained by adding oil and polypropylene (PP) to adjust the hardness to a styrene-ethylene-butylene-styrene block copolymer (SEBS) is used.
[0003]
[Problems to be solved by the invention]
In the composition, in order to obtain an appropriate low hardness, a large amount of oil must be used as a softening agent, and a molded article using the composition, for example, the cabinet (1) is used for a long time. If left on the cloth, the oil may breathe.
[0004]
[Means for Solving the Problems]
The present invention provides a styrene-ethylene-butylene-styrene block copolymer elastomer, a styrene-ethylene-propylene-styrene block copolymer, and a styrene-ethylene-propylene block copolymer as means for solving the above conventional problems. 4 the combined: 6 to 6: a mixture of 4 weight ratio, a 2: 8 to 8: 50 to 80 parts by weight oil to 100 parts by weight of the mixture were mixed with double amount ratio, the addition of polypropylene 10-20 parts by weight An elastomer composition is provided.
It is preferable that a portion of the oil has been substituted by the low molecular resin, said polypropylene flexural modulus is preferably a random polypropylene 600～800MPa.
Further, the present invention provides a cabinet in which the main body is made of a hard thermoplastic resin and the corners are made of the elastomer composition, and the cabinet is preferably a hard disk cabinet.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below. The composition of the present invention comprises a styrene-ethylene-butylene-styrene block copolymer elastomer (SEBS), a styrene-ethylene-propylene-styrene block copolymer (SEPS), and a styrene-ethylene-propylene block copolymer (SEP). ) and 4: 6 to 6: a mixture of 4 weight ratio, a 2: 8 to 8: to a mixture 100 parts by weight were mixed in a double amount ratio, the oil 50 to 80 parts by weight of polypropylene (PP) 10 to 20 A part by weight is added.
The elastomer component of the present invention, the SEBS as described above, the combined use of SEPS and SEP, the S EPS and SEP 4: 6 to 6: to use a mixture of 4 weight ratio.
[0006]
The SEPS and SEP increase the flexibility of SEBS and reduce the amount of oil added, thereby preventing the oil from breathing from the composition.
[0007]
The SEBS has a molecular weight of about 100,000 to 200,000 and a hardness (A) of about 70 to 80. The SEPS: SEP mixture is a 1: 1 weight ratio mixture and has a hardness (A) of 30 to 30. 40 are preferably used. SEP has a lower hardness than SEPS and improves the moldability of SEPS.
[0008]
The oil used in the present invention is usually used as a plastic softener such as paraffinic or aromatic mineral oil, silicone oil, vegetable oil or the like.
Further, a part of the oil may be substituted with a low molecular weight resin such as a low molecular weight terpene resin, hydrogenated terpene resin, rosin, rosin derivative, petroleum resin, alkylphenol resin, xylene resin, coumarone indene resin. By substituting part of the oil with such a low-molecular resin, the amount of oil added can be reduced, so that oil bleeding from the composition can be prevented.
[0009]
As the PP, a homo-PP having a high crystallinity which has been conventionally used can be used, but a random PP having a low crystallinity is preferably used. Random PP has a lower elastic modulus than homo PP, and can impart an appropriate low hardness, for example, hardness (A) of 30 to 45, to the composition. For example, those having a flexural modulus of 1200 to 2000 MPa are used as the homo PP, and those having a flexural modulus of 500 to 800 MPa are used as the random PP.
[0010]
In addition to the above components, the composition of the present invention includes, for example, talc, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, calcium sulfite, calcium phosphate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, magnesium oxide, titanium oxide. , Iron oxide, zinc oxide, alumina, silica, diatomaceous earth, dolomite, gypsum, calcined clay, asbestos, mica, calcium silicate, bentonite, white carbon, carbon black, iron powder, aluminum powder, stone powder, blast furnace slag, fly Inorganic fillers such as ash, cement and zirconia powder, organic fillers such as linter, linen, sisal, wood powder, palm powder, walnut powder, starch and wheat flour, or natural fibers such as cotton, hemp and wool, polyamide fibers , Polyester fiber, acrylic fiber, biscoe Fibers, organic fiber such as acetate fiber, asbestos fiber, glass fiber, carbon fiber, ceramic fiber, metal fiber, fiber filler such as inorganic fiber such as whisker, pigment, dye, heat stabilizer, light stabilizer, plasticizer , Antioxidants, antistatic agents, flame retardants, flame retardants, insecticides, preservatives, waxes, lubricants, anti-aging agents, UV absorbers and other additives, or a mixture of two or more Also good.
[0011]
The composition of the present invention is kneaded by, for example, a Banbury mixer, an open roll calender, etc., and is usually extruded into a strand shape by an extruder, and cut into a pellet by a cutter in a cooling water tank.
The pellets of the above composition are usually molded by injection molding or the like to form a molded product. For example, the box (2,3) of the cabinet (1) is first injection molded of the main body (4,5) with PP or the like. Subsequently, the corner portion (6, 7) is manufactured by the so-called two-color molding method by injection molding with the composition of the present invention.
Examples of the present invention are shown below.
[0012]
〔Example〕
The compositions of Examples 1, 2, 3, and 4 and the compositions of Comparative Examples 1, 2, and 3 are prepared with the compositions shown in Table 1. A 125 × 125 × 2 mm plate test piece was injection-molded with the composition of each example and comparative example, and the performance was tested using each test piece. The results are shown in Table 1.
[0013]
[Table 1]
[0014]
〔Test method〕
Hardness (A): Measured according to JISK6253 A type method.
Compression permanent strain (CS): JIS K6262 (25% deformation).
Oil bleed: A test piece was placed on paper, and a weight of 1 kg / cm ² was applied for 3 days, and the presence or absence of oil bleed (migration) was visually confirmed.
○: No transition Δ: Some transition X: Significant transition Moldability: Judged by the degree of shrinkage after injection molding.
○: Small contraction △: During contraction ×: Large contraction
Referring to Table 1, in Examples 1, 2, 3, and 4 using the composition of the present invention, the oil addition amount is 56 to 80 parts by weight, the hardness (A) is 34 to 40, and the oil is oil. There was no migration at all and the moldability was good. In Comparative Example 1 using only SEBS, it was necessary to add 170 parts by weight of oil in order to obtain a low hardness (A) 37, and significant oil transfer was observed. In Comparative Example 2 where SEBS: SEPS / SEP was 90:10 weight ratio, 150 parts by weight of oil had to be added in order to obtain a low hardness (A) of 35, and significant oil transfer was observed. Furthermore, in Comparative Example 3 in which the SEBS: SEPS / SEP ratio is 10:90, the amount of oil added to make the low hardness (A) 37 is sufficient as 30 parts by weight, but the compression set is as large as 95%. Formability is not very good. The compression set is preferably 80% or less.
[0016]
【The invention's effect】
When the composition of the present invention is used, a molded product having low hardness and not causing oil breathing can be obtained.
[Brief description of the drawings]
FIG. 1 is a perspective view of a cabinet.
1 cabinet
2,3 box
4,5 Body part
6,7 Corner

Claims (5)

A mixture of 4 weight ratio: styrene - styrene block copolymer elastomer, styrene - - ethylene - butylene 4 of propylene block copolymer ethylene - propylene - styrene block copolymer and styrene - - Ethylene: 6 to 6 2: 8 to 8: 50 to 80 parts by weight oil to 100 parts by weight of the mixture were mixed with double amount ratio, elastomeric composition, characterized in that the addition of polypropylene 10 to 20 parts by weight. The elastomer composition according to claim 1, wherein a part of the oil is replaced by a low molecular resin . The elastomer composition according to claim 1 or 2 , wherein the polypropylene is a random polypropylene having a flexural modulus of 600 to 800 MPa . A cabinet comprising a main body made of a hard thermoplastic resin and a corner portion made of the elastomer composition according to any one of claims 1 to 3 . The cabinet according to claim 4 , wherein the cabinet is a cabinet for a hard disk .