JP5102462B2 - Composite sheet - Google Patents

Description

The present invention relates to a composite sheet and a molded body for packaging in which the sheet is secondarily formed.

Polypropylene-based resin sheets are excellent in heat resistance and solvent resistance, do not generate resin shavings due to friction, and are excellent in wear resistance, so they are suitable for packaging of electronic parts and foods. Yes. However, on the other hand, polypropylene resins have lower rigidity than polystyrene resins and it is difficult to impart antistatic properties.
Various proposals have been made as methods for improving these, and as a method for improving the rigidity, talc, calcium carbonate or the like is generally added as a filler to a polypropylene resin. In addition, as a method for imparting antistatic properties, a method of applying an antistatic agent to the surface of a sheet or a package, a method of blending a conductive filler such as carbon black in a resin, and an antistatic agent such as a surfactant. It is widely known that an agent is added to a resin.

As an example, Patent Document 1 proposes a composite sheet in which a polypropylene resin composition film or sheet containing carbon black is laminated on one or both sides of a resin composition sheet base material composed of a polypropylene resin and a filler. . However, when carbon black is used as the conductive filler, when used as a package, the surface of the sheet is scraped from the friction between the contents of the electronic components and the package due to vibration during transportation, etc. There was a problem of being contaminated with the conductive resin contained.
This problem is becoming more prominent in the form of electrical failure due to the downsizing and increasing the density of electronic components. Patent Document 2 proposes a laminated sheet using a polymer antistatic agent as a countermeasure. Yes. The laminated sheet proposed in Patent Document 2 solves the above-mentioned rigidity problem, but there is a problem that when the composite sheet is thermoformed, a molded product having a uniform sheet thickness cannot be obtained. there were.
Japanese Patent Publication No. 05-8097 JP 2005-28771 A

The present invention is excellent in rigidity, has a sufficient antistatic effect, and is particularly excellent in obtaining a molded product having a uniform thickness distribution when thermoforming a composite sheet (hereinafter referred to as deep drawability). A composite sheet is provided.

As a result of earnestly examining the means for solving the above problems, the present inventors have blended a polymer-type antistatic agent with a polyolefin-based resin as a surface layer, so that the antistatic performance does not deteriorate even when washed with water or wiped off, for a long time. A sufficient antistatic effect was obtained over a long period of time, and a multilayer structure was adopted from the viewpoint of rigidity, and the present invention was completed by blending a specific polyolefin resin and a specific amount of filler as a base material layer.
That is, the present invention is as follows.
(1) 15-50 parts by mass of a filler is contained in 100 parts by mass of a polyolefin resin consisting of 50-20 parts by mass of a polypropylene resin and 50-20 parts by mass of a polyethylene resin having a Vicat softening point of 80-130 ° C. On one or both sides of the resulting base material layer (A), 98 to 50 parts by mass of a polypropylene resin and 100 parts by mass of a polyolefin resin consisting of 2 to 50 parts by mass of a polyethylene resin, and 10 to 30 masses of a polymeric antistatic agent The composite sheet which has the surface layer (B) formed by containing a part.
(2) The composite sheet according to claim 1, wherein the polymer antistatic agent contains a block polymer of polyolefin and polyether.
(3) The composite sheet according to any one of claims 1 and 2, wherein the surface resistivity of the surface layer (B) is 10 ⁸ Ω or more and less than 10 ¹² Ω.
(4) The ratio of the surface layer (B) with respect to the total thickness of a composite sheet is 2 to 15% on one side, The composite sheet according to any one of claims 1 to 3.
(5) A molded article for packaging comprising the composite sheet according to any one of claims 1 to 4.

ADVANTAGE OF THE INVENTION According to this invention, the composite sheet excellent in the antistatic property, rigidity, and the deep drawability at the time of secondary-molding a composite sheet can be provided.

The present invention will be described in detail below.
The polypropylene resin used for the base material layer and the surface layer is a homopolymer of propylene or a copolymer containing propylene as a main component, and these resins that are generally commercially available can be used alone or in combination. is there. As the copolymer mainly composed of propylene, a random or block copolymer of propylene and one or more selected from ethylene and α-olefin can be used. Examples of the α-olefin include 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and the like.

The polyethylene-based resin is a homopolymer of ethylene or a copolymer having ethylene as a main component, and these resins that are generally available on the market can be used alone or as a mixture, but as a specific example, , Linear low density polyethylene (L-LDPE), low density polyethylene (LDPE), very low density polyethylene (VLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE) and the like. Specific examples of the copolymer having ethylene as a main component include ethylene / ethyl acrylate copolymer (EEA), ethylene vinyl acetate copolymer, and the like. Among these, high density polyethylene (HDPE) is preferable because it has a high effect of improving processability when a sheet is formed.
Among the polyethylene resins, the polyethylene resin used for the base material layer has a Vicat softening point of 80 to 130 ° C, preferably 90 to 125 ° C. If the Vicat softening point is less than 80 ° C., the workability at the time of molding the sheet is lowered, and if it exceeds 130 ° C., the deep drawability at the time of secondary molding is lowered.
The polyethylene resin used for the surface layer can be used regardless of the Vicat softening point, but preferably has a Vicat softening point of 80 to 130 ° C, more preferably 90 to 125 ° C.

The compounding ratio of the polypropylene resin of the base material layer and the polyethylene resin having a Vicat softening point of 80 to 130 ° C is 50 to 80 parts by mass of the polypropylene resin and the polyethylene resin 50 to 80 of Vicat softening point. 20 parts by mass is preferable, and 60 to 78 parts by mass of a polypropylene resin and 40 to 22 parts by mass of a polyethylene resin having a Vicat softening point of 80 to 130 ° C are more preferable. The polyethylene-based resin has an effect of improving processability when molding a sheet. If the amount is less than 20 parts by mass, the effect may not be sufficiently obtained. If the amount exceeds 50 parts by mass, mechanical properties such as sheet rigidity are obtained. May be damaged.

As the filler, various inorganic fillers can be used, but at least one selected from talc, glass fiber, mica, and calcium carbonate is preferably used, and talc is particularly preferable. The average particle size of talc is preferably in the range of 5 to 30 μm, more preferably in the range of 8 to 20 μm. If the average particle size of talc is less than 5 μm, the talc dispersibility may be reduced during extrusion of the sheet. If it exceeds 30 μm, pinholes may be formed during sheet formation or when the sheet is secondarily formed into a packaging container. It tends to occur. The average particle diameter was measured with “Slurry Particle Size Analyzer SALD-2000J manufactured by Shimadzu Seisakusho Co., Ltd.” in accordance with JIS R 1629 (Method for measuring particle diameter distribution by laser diffraction / scattering method of fine ceramic raw material). The average particle size was calculated by multiplying the value of each particle size by the relative particle amount (difference%) and dividing by the total relative particle amount (100%).
Moreover, as addition amount of a filler, 15-50 mass parts is preferable. If the addition amount is less than 15 parts by mass, the effect is not sufficient, and if it exceeds 50 parts by mass, the workability when extruding the sheet may be impaired.

The polymeric antistatic agent is an antistatic agent in which at least one monomer unit has a large number of repeating chain structures due to chemical bonds, and the molecular weight is generally 1000 or more.
Examples of polymer antistatic agents include polyether ester amide, block polymer of polyolefin and polyether, polyamide as the backbone polymer, graft polymer consisting of block polymer of polyalkylene ether and polyester as branch polymer, caprolactam, imide ring A polyhydric carboxylic acid component, a copolymer of organic diisocyanate and polyethylene glycol, a copolymer of α-olefin, maleic anhydride and polyalkylene allyl ether, a polymer of polyethylene ether, isocyanate and glycol, etc. By using at least one of these, a long-lasting antistatic effect can be obtained. Among these, polyolefin and polyether block polymers are preferable because sufficient antistatic effects can be obtained with a small amount of use compared to other polymer antistatic agents.

  The surface layer of the present invention is formed on one side or both sides of the base material layer, and the polymer type antistatic agent 10-30 for a total amount 100 of 98-50 parts by mass of polypropylene resin and 2-50 parts by mass of polyethylene resin. The resin composition formed by blending parts by mass is used. If necessary, a small amount of a graft polymer of unsaturated acid anhydride and polyolefin may be added in order to improve the compatibility between the polyolefin resin and the polymer type antistatic agent.

The compounding ratio of the polypropylene resin and the polyethylene resin in the surface layer is preferably 98 to 50 parts by mass of the polypropylene resin and 2 to 50 parts by mass of the polyethylene resin, 95 to 65 parts by mass of the polypropylene resin and 5 to 35 parts by mass of the polyethylene resin. Part is more preferred. Polyethylene resin has the effect of improving processability when molding a sheet, and if it is less than 2 parts by mass, the effect may not be sufficiently obtained. If it exceeds 50 parts by mass, the mechanical properties such as sheet rigidity are obtained. May be damaged.

The amount of the polymeric antistatic agent used for the surface layer is preferably 10 to 30 parts by mass, and more preferably 12 to 20 parts by mass with respect to 100 parts by mass of the total amount of the polypropylene resin and the polyethylene resin. If it is less than 10 parts by mass, a sufficient antistatic effect may not be obtained. If it exceeds 30 parts by mass, the appearance and wear resistance of the sheet and the molded product may be reduced.

The surface resistivity of the composite sheet of the present invention is 10 ⁸ Ω or more and less than 10 ¹² Ω. When the surface resistivity is 10 ¹² Ω or more, the sheet and the molded body thereof are easily charged, and thus cannot be suitably used for packaging electronic components that are easily affected by static electricity.

On the surface layer, various stabilizers such as light stabilizers, ultraviolet absorbers, antioxidants, plasticizers, lubricants, colorants, foaming agents, etc., as long as the physical properties, film-forming properties and secondary moldability of the sheet are not excluded. A processing aid or the like can be added as necessary.

Although the thickness of the composite sheet of this invention is not specifically limited, A 0.1 mm-2 mm sheet | seat is used suitably, More preferably, it is 0.3 mm-1.5 mm. Further, the ratio of the surface layer to the total thickness of the composite sheet is preferably 2 to 15% on one side.

For the base material layer, various stabilizers such as light stabilizers, ultraviolet absorbers, antioxidants, plasticizers, lubricants, colorants, foaming agents, as long as the physical properties, film-forming properties and secondary moldability of the sheet are not excluded. It is possible to add a processing aid such as

In order to manufacture the composite sheet of the present invention, first, each component of the base layer and the surface layer is individually blended at a predetermined ratio, and then dry blended with a mixer such as a commonly used tumbler. Alternatively, some or all of the components are kneaded with a twin screw extruder or the like to obtain 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 composite sheet can be obtained by a known method such as an extruder or calendar molding. The method of laminating each layer of the sheet can be laminated in stages by extrusion laminating method, dry laminating method, thermal laminating method, etc. after forming each into a film or sheet by a separate extruder, It is possible to laminate other layers on a preformed base sheet by a method such as extrusion coating, but in order to manufacture at a lower cost, a multilayer coextrusion method using a feed block or a multi-manifold die It is preferable to obtain a composite sheet in a batch.

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

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited by these. In the examples and comparative examples, various performances were evaluated by the following methods.
(1) Tensile properties Evaluation was performed according to JIS K 7127.
(2) DuPont impact strength Evaluation was performed according to ASTM D-2794.
(3) Surface resistivity It evaluated based on JISK6911.
(4) Sheet film forming cooling roll temperature was 80 ° C., and when film was formed into a sheet, a film that caused adhesion to the cooling roll was determined to be defective, and a sheet that did not generate was determined to be good.
(5) Formability Each container was formed into a container (360 × 260 mm) having the following four cup shapes and two truncated pyramid shapes with a single molding machine (manufactured by Asano Laboratories). The molded product was evaluated by generating wrinkles (bridges) by drawdown, and evaluating how many wrinkles were generated in 10 molded products. One with one or more wrinkles was regarded as defective, and one with no wrinkles was defined as good.
Cup shape (flange diameter: 40 mm, bottom diameter: 30 mm, height: 45 mm)
Pyramidal shape (flange: 40 mm x 80 mm, bottom: 30 mm x 70 mm, height: 45 mm)
(6) Deep drawability Ten molded products were molded from each sheet using a female mold having an inner diameter of 96 mm and a height of 48 mm using a single molding machine manufactured by Asano Laboratories. In all of the 10 molded products, those having a good shape and having no tears or the like on the side portion or the bottom portion were good, and those in which any abnormality was recognized even in one were regarded as bad.

(Examples 1 to 4, 6, 7, Experimental Examples 1 and 2 )
The base layer resin and the surface layer resin were blended with a tumbler according to the formulation shown in Table 1. After blending, the layers shown in Table 1 by a feed block method using one 65 mm diameter extruder (L / D = 32), two 40 mm diameter extruders (L / D = 26) and a 600 mm wide T-die. A sheet having a thickness of 1 mm was obtained at a composition ratio.
Tables 1 and 2 show the types of materials used. In addition, the average particle diameter of the talc used for the base material layer was 12 (μm).

(Comparative Examples 1-7)
A sheet having a thickness of 1 mm was obtained in the same manner as in Example except that the composition and the layer constitution ratio were as shown in Table 2.

Table 3 shows the evaluation results of Examples and Experimental Examples , and Table 4 shows the evaluation results of Comparative Examples.
MD in Table 3 indicates the sheet extrusion direction, and TD indicates the sheet width direction.

The composite sheet provided by the present invention is excellent in rigidity, has a sufficient antistatic effect, and is particularly excellent in deep drawability when the composite sheet is subjected to secondary forming such as vacuum forming.

Claims (3)

  Base material layer comprising 15 to 50 parts by mass of talc in 100 parts by mass of polyolefin resin comprising 60 to 78 parts by mass of polypropylene resin and 40 to 22 parts by mass of polyethylene resin having a Vicat softening point of 90 to 130 ° C. A polymer comprising a polyolefin and polyether block polymer in 100 parts by mass of a polyolefin resin comprising 95 to 65 parts by mass of a polypropylene resin and 5 to 35 parts by mass of a polyethylene resin on one or both sides of (A). It has a surface layer (B) containing 10 to 30 parts by weight of a type antistatic agent, the total thickness is 0.1 to 2 mm, and the ratio of the surface layer (B) to the total thickness is 2 to 15 on one side % Composite sheet for packaging electronic components. The composite sheet according to claim 1 , wherein the surface resistivity of the surface layer (B) is 10 ⁸ Ω or more and less than 10 ¹² Ω. For packaging electronic components molded body made of a composite sheet according to claim 1 or 2.