JP2006116888A - Composite sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet or the like which has little change in a surface resistance value even if it is left for a long period of time, furthermore in which even a carrier tape and a tray which are obtained by forming the sheet has a sufficient antistatic property. <P>SOLUTION: The composite sheet comprises an epidermal layer comprising a styrene resin including a graft rubber component, a styrene-conjugated diene block copolymer of 3-20 mass% having a conjugated diene content of 5-40 mass%, and a surface active agent of 0.4-4 mass% which is laminated on at least one surface of a substrate layer which consists primarily of a styrene resin including a graft rubber component. Further, the substrate layer preferably comprises a resin composition which consists primarily of a styrene resin including a graft rubber component and a styrene-conjugated diene block copolymer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a composite sheet having antistatic properties.

Electronic components are stored in electronic component packaging containers such as carrier tapes and trays for use. In such applications, it is often necessary to prevent functional failure due to static electricity of electronic components to be stored, and for example, antistatic measures such as using a resin tape containing a conductive filler are taken. However, depending on the electronic component to be stored, it may not be preferable to use the conductive filler as described above. For such applications, those using styrene-based resins are often used from those based on conventional vinyl chloride resins (see, for example, Patent Documents 1 to 4). Even in such a case, when it is necessary to suppress functional failure due to static electricity of the stored electronic components, these packaging containers are subjected to antistatic treatment. Various methods are used for the antistatic treatment depending on the required level, but surfactants are often used as an inexpensive method that does not impair the mechanical properties of the sheet.
JP-A-8-12847 JP-A-9-151285 Japanese Patent Laid-Open No. 10-279755 JP 2002-331621 A

  However, when a surfactant is used for the styrene resin, a surface resistance value sufficient to suppress functional failure due to static electricity may not be obtained. That is, even if the sheet has a sufficient surface resistance value, the carrier tape or tray obtained by molding the sheet does not provide a sufficient surface resistance value. Otherwise, there is a problem that the surface resistance value increases. The present invention solves such a problem, and provides a sheet having a sufficient antistatic property even in a carrier tape or a tray obtained by molding a sheet with little change in surface resistance value even when left for a long period of time. It is.

That is, the present invention comprises a composition comprising the following components (a) to (c) on at least one surface of a base material layer mainly composed of a styrene-based resin containing a graft rubber component. When the whole is 100%, this is a composite sheet in which a skin layer containing 3 to 20% by mass of component (b) and 0.4 to 4% by mass of component (c) is laminated.
(A) Styrenic resin containing a graft rubber component (b) Styrene-conjugated diene block copolymer having a conjugated diene content of 5 to 40% by mass (c) Surfactant

  Furthermore, the base material layer is preferably composed of a resin composition containing a styrene resin containing a graft rubber component and a styrene-conjugated diene block copolymer as main components. Furthermore, the present invention is a container made of the composite sheet or a tray for packaging electronic parts.

  Laminate a skin layer containing styrene resin containing graft rubber, styrene-conjugated diene block copolymer and surfactant as main components on at least one side of the base material layer containing styrene resin containing graft rubber as the main component. By doing so, it is possible to obtain antistatic properties that have a surface resistance value sufficient to suppress functional failure due to static electricity and that are excellent in stability of the surface resistance value over a long period of time.

  The styrene resin referred to in the present invention is styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, 1,1. -A resin mainly composed of a polymer containing an aromatic vinyl compound such as diphenylethylene as a monomer.

  In the present invention, (a) a styrene resin containing a graft rubber component is a styrene resin containing a graft rubber obtained by graft polymerization of an aromatic vinyl such as styrene on a rubber such as polybutadiene, and is generally resistant to resistance. The main component is a resin called impact polystyrene (HIPS) resin. Further, a mixture of this HIPS and a general polystyrene (GPPS) resin may be used, but this mixture is also abbreviated as HIPS resin hereinafter.

  The graft ratio of the graft rubber of the HIPS resin used in the present invention is preferably 1.8% or more, more preferably 2.0 to 2.5% in both the base material layer and the skin layer. The swelling ratio of the graft rubber is preferably 13 or less. When the graft ratio or the swelling ratio is out of this range, the impact strength is lowered.

  The content of the graft rubber in the HIPS resin used for the base material layer and the skin layer is preferably 4.0% by mass or more and 20% by mass or less. If it is less than 4.0% by mass, the impact strength is lowered, and if it exceeds 20% by mass, the rigidity of the sheet may be lowered.

In the present invention, the amount of the graft rubber in the HIPS resin can be measured by a halogen addition method or the like. The graft ratio can be determined from the gel content (mass%) and the graft rubber content (mass%) in the resin as follows.
Graft rate = (gel content-graft rubber content) / graft rubber content

The graft rubber content in the HIPS resin can be obtained by dissolving the HIPS resin in chloroform, adding a certain amount of iodine monochloride / carbon tetrachloride solution and leaving it in the dark for about 1 hour, and then adding a potassium iodide solution. Iodine monochloride is titrated with 0.1N sodium thiosulfate / ethanol aqueous solution, and can be determined from the amount of iodine monochloride added. The gel content in the HIPS resin is obtained by dissolving the mass (W) of the HIPS resin in methyl ethyl ketone at a ratio of 5% by mass, centrifuging the solution to settle the insoluble content, and removing the supernatant by decantation. Insoluble matter was obtained, vacuum-dried at 70 ° C. for 15 hours, cooled in a desiccator for 20 minutes, and then the mass (G) of the dried insoluble matter was measured and determined as follows.
Gel content (mass%) = (G / W) × 100

Further, the degree of swelling of the graft rubber is obtained by dissolving the resin composition in toluene, centrifuging the solution to settle the insoluble matter, removing the supernatant by decantation, and the mass of the insoluble matter swollen with toluene (S) Measure. Next, the insoluble matter swollen with toluene is vacuum-dried at 70 ° C. for 15 hours, cooled in a desiccator for 20 minutes, and then the dry mass (D) of the insoluble matter is measured to obtain as follows.
Swelling degree = S / D

  The volume average rubber particle diameter of the HIPS resin used for the base material layer and the skin layer in the present invention is preferably 1.0 μm or more and 3.5 μm or less, more preferably 1.3 μm or more and 3.2 μm or less. A rubber particle system having this range is excellent in transparency. The rubber particle size can be determined by dissolving a resin in dimethylformamide and measuring it with a laser diffraction particle size distribution measuring device, and can be calculated from a volume-based particle size distribution curve.

  In the present invention, the styrene-conjugated diene block copolymer added to the skin layer or the base material layer is mainly composed of a polymer block mainly composed of a styrene monomer and a conjugated diene monomer in the structure. A polymer containing a polymer block. Styrene monomers include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, 1,1-diphenylethylene Among them, styrene is preferable. One or more styrenic monomers can be used. The conjugated diene monomer is a compound having a conjugated double bond in its structure. For example, 1,3-butadiene (butadiene), 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl- There are 1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 2-methylpentadiene, etc., among which butadiene and isoprene are preferred. One type or two or more types of conjugated diene monomers can be used.

  A polymer block mainly composed of a styrene monomer, a polymer block consisting only of a structure derived from a styrene monomer, and a polymer block containing 50% by mass or more of a structure derived from a styrene monomer Means either. A polymer block mainly composed of a conjugated diene monomer is a polymer block consisting only of a structure derived from a conjugated diene monomer, or a polymer block containing 50% by mass or more of a structure derived from a conjugated diene monomer. It means both.

  The type of (c) surfactant used in the present invention is not particularly limited, and cationic, anionic and amphoteric ionic surfactants and nonionic surfactants can be used. In order to obtain the surface resistance value, it is preferable to use an ionic surfactant. In the ionic surfactant, anionic surfactants are preferably used because cationic and amphoteric surfactants have poor heat resistance.

  The skin layer of the composite sheet of the present invention is composed of a composition comprising the HIPS resin, styrene-conjugated diene block copolymer, and a surfactant. The proportion of the styrene-conjugated diene block copolymer in the composition constituting the skin layer is 3 to 20% by mass. If the proportion of the styrene-conjugated diene block copolymer is less than this, a sufficient surface resistance value cannot be obtained, and conversely if it is too large, the long-term stability of the surface resistance value is lowered. Moreover, the conjugated diene content in the polymer of the styrene-conjugated diene block copolymer (b) used for the skin layer is in the range of 5 to 40% by mass, preferably 10 to 30% by mass. Conjugated diene content means the ratio of the mass which occupies in all the copolymers of the structure derived from a conjugated diene monomer. If the conjugated diene content is less than this range, a sufficient surface resistance value cannot be obtained. Conversely, if the conjugated diene content is too large, the long-term stability of the surface resistance value is lowered. One type or two or more types of styrene-conjugated diene block copolymers can be used. A commercially available styrene-conjugated diene block copolymer can also be used as it is.

  The ratio of the surfactant with respect to the entire composition of the skin layer is 0.4 to 4.0% by mass, preferably 0.6 to 2.5% by mass. If the ratio of the surfactant is less than this range, the surface resistance value cannot be obtained sufficiently, and if it is too large, the surface of the sheet or molded product may become sticky, which may contaminate the non-packaged product.

  On the other hand, the base material layer of the present invention can use HIPS resin alone, but when the total resin is 100, styrene-conjugated diene block copolymer is added in the range of 2 to 40% by mass. It is preferable to do. By adding the styrene-conjugated diene copolymer, the formability at the time of thermoforming the sheet is improved, and a packaging container having a more complicated shape can be obtained. If the addition amount of the styrene-conjugated diene block copolymer is less than 2% by mass, a sufficient effect may not be obtained, and if it exceeds 40% by mass, the rigidity of the sheet may be lowered.

  In the resin composition used for the skin layer and the base material layer of the present invention, a processing aid represented by a lubricant such as an antioxidant, a UV absorber, a deterioration inhibitor, an internal lubricant, an external lubricant, etc. In addition to the agent, it is also possible to add a small amount of other resin components as a modifier.

  In order to produce the sheet of the present invention, first, each component of the base material layer and the skin layer is individually blended at a predetermined ratio, and dried using a mixer such as a tumbler generally used. Blending or kneading all or part of the components with a twin screw extruder or the like gives a pellet-like compound. When obtaining a dry blend or pellet compound, there is no particular restriction on the order of addition of each component.

  The sheet can be obtained by a known method using an extruder, calendar molding or the like. As a method of laminating each layer of the sheet, it is possible to form each in a sheet or film form with a separate extruder, and then laminate in stages by a thermal laminating method, a dry laminating method, an extrusion laminating method, etc. Other layers can be laminated on the preformed sheet base layer by methods such as extrusion coating, but multilayer coextrusion using a multi-manifold die or feed block can be manufactured at a lower cost. It is preferable to obtain a laminated sheet collectively by the method.

  Although the thickness of a sheet | seat is not specifically limited, A 50 micrometers-2000 micrometers sheet | seat is used suitably. Moreover, as for the ratio of the skin layer to the whole sheet | seat, 2 to 15% of each one side is preferable. If the thickness of the skin layer is less than this range, the long-term stability of the surface resistance value is poor, and if it exceeds this range, the cost increases.

  By using a known sheet forming method such as vacuum forming, pressure forming, or press forming from the sheet, an electronic component packaging container having a free shape can be obtained.

  There are no particular limitations on the electronic components to be packaged. For example, IC, LED (issuing diode), resistor, liquid crystal, capacitor, transistor, piezoelectric element register, filter, crystal oscillator, crystal resonator, diode, connector, switch, volume, There are relays and inductors. The format of the IC is not particularly limited, and examples thereof include SOP, HEMT, SQFP, BGA, CSP, SOJ, QFP, and PLCC. In addition, intermediate products and final products that use these electronic components are subject to packaging.

The present invention will be described more specifically with reference to examples. In these examples, various performances were evaluated by the following methods.
(1) Surface resistivity The surface resistivity was measured in a 23 ° C. × 50% RH environment according to JIS K 6911 using the sheets of the examples and comparative examples. Moreover, about the long-term stability of surface resistivity, the same measurement was performed after leaving still for 6 months in 23 degreeC x 50% RH environment.
(2) Formability Using the sheets of each Example and Comparative Example, a round cup container having a drawing ratio of 0.5 and 1.0 was formed by a single vacuum forming machine, and the thickness of the bottom portion was measured.
(3) Surface resistivity of molded product Using the sheets of the examples and comparative examples, a round cup container with a drawing ratio of 0.5 was molded with a single-shot vacuum molding machine, and the surface resistivity at the bottom was JIS K. It was measured in an environment of 23 ° C. × 50% RH in accordance with 6911.

Example 1
The base layer resin and the skin layer resin were blended with a tumbler at the following composition ratios, and then kneaded with a φ45 mm twin screw extruder to obtain a compound of each resin composition.
Base material layer: 20% by mass of GPPS as a polystyrene resin, impact-resistant polystyrene resin (low-sis rubber, graft rate 2.2%, graft rubber content 9.8%, rubber particle diameter 2.5 μm, rubber swelling 11) 80 mass %
(Graft rubber content in the base material layer is 7.8% of the resin composition)
Skin layer: 6% by mass of GPPS as a polystyrene resin, high-impact polystyrene resin (low-sis rubber, graft rate 2.2%, graft rubber content 9.8%, rubber particle diameter 2.5 μm, rubber swelling 11) 82% by mass , Styrene-butadiene block copolymer (styrene content 74% by mass, conjugated diene content 26% by mass of butadiene-based polymer block) 10% by mass, anionic surfactant 2% by mass
Next, one φ65 mm extruder (L / D = 32), two φ40 mm extruders (L / D = 26) and a 600 mm wide T-die by the FB block method, a wall thickness of 1 mm and a layer composition ratio of 10:80 : Two types and three layers of 10 were obtained.

(Example 2)
A sheet having a thickness of 1 mm was obtained in the same manner as in Example 1 except that the composition ratio of the resin of the base material layer was as follows.
Base material layer: As polystyrene resin, the same high-impact polystyrene resin as in Example 1, 97% by mass, styrene-butadiene block copolymer (styrene content 80% by mass, conjugated diene content 20 in butadiene-based polymer block 20 Mass%) 3 mass%
(Graft rubber content in the base material layer is 9.5% of the resin composition)

(Example 3)
A sheet having a thickness of 1 mm was obtained in the same manner as in Example 1 except that the ratio of the resin composition of the base material layer was as follows.
Base material layer: As polystyrene resin, the same high-impact polystyrene resin as in Example 1, 95% by mass, styrene-butadiene block copolymer (styrene content 40% by mass, conjugated diene content 60 of polymer block mainly composed of butadiene) Mass%) 5 mass%
(Graft rubber content in the base material layer is 9.3% with respect to the resin composition)

(Comparative Example 1)
A sheet having a thickness of 1 mm was obtained in the same manner as in Example 1 except that the blending ratio of the composition of the skin layer was as follows.
Skin layer: 6% by mass of GPPS as polystyrene resin, 92% by mass of impact-resistant polystyrene resin as in Example 1, 2% by mass of anionic surfactant

(Comparative Example 2)
As in Example 1, except that the styrene-butadiene block copolymer in the skin layer was a styrene content of 40% by mass and a butadiene-based polymer block having a conjugated diene content of 60% by mass. Thus, a sheet having a thickness of 1 mm was obtained.

(Comparative Example 3)
A sheet having a thickness of 700 μm was obtained in the same manner as in Example 1 except that the blending ratio of the composition in the skin layer was as follows.
Skin layer: 7.7 mass% of GPPS as a polystyrene resin, the same impact-resistant polystyrene resin as in Example 1 (low-sis rubber, graft ratio 2.2%, graft rubber content 9.8%, rubber particle diameter 2.5 μm, rubber Swelling degree 11) 82% by mass, 10% by mass of the same styrene-butadiene block copolymer as in Example 1, 0.3% by mass of an anionic surfactant
(Comparative Example 4)
A sheet having a thickness of 1 mm was obtained in the same manner as in Example 1 except that the ratio of the composition in the skin layer was as follows.
Skin layer: 6 parts by mass of GPPS as a polystyrene resin, 32 parts by mass of the same impact-resistant polystyrene resin as in Example 1) 60 parts by mass of the same styrene-butadiene block copolymer as in Example 1 and 2 parts by mass of an anionic surfactant %

  The evaluation results of each example and comparative example are shown in Table 1.

Claims (4)

At least one surface of a base material layer mainly composed of a styrene resin containing a graft rubber component is composed of a composition composed of the following components (a) to (c), and the entire composition is 100% A composite sheet in which a skin layer containing 3 to 20% by mass of component (b) and 0.4 to 4% by mass of component (c) is laminated.
(A) Styrenic resin containing a graft rubber component (b) Styrene-conjugated diene block copolymer having a conjugated diene content of 5 to 40% by mass (c) Surfactant   The composite sheet according to claim 1, wherein the base material layer is made of a resin composition containing a styrene resin containing a graft rubber component and a styrene-conjugated diene block copolymer as main components.   A container comprising the composite sheet according to claim 1.   An electronic component carrying tray comprising the composite sheet according to claim 1.