JP4520868B2 - Composite sheet - Google Patents

Description

  The present invention relates to an antistatic polyolefin-based resin composite sheet and a packaging molded body obtained by secondary molding the sheet by a method such as vacuum forming. Specifically, the antistatic polyolefin-based resin has stable antistatic properties, does not generate abrasion powder due to rigidity and friction (hereinafter referred to as abrasion resistance), and has excellent protection performance particularly as a packaging body for electronic parts. The present invention relates to a composite sheet and a molded body such as a container obtained by thermoforming the composite sheet.

  Polypropylene-based resin sheets are excellent in heat resistance and solvent resistance, and are excellent in wear resistance, and thus are suitably used for packaging bodies such as electronic parts and foods. 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 of 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, or a charging of a surfactant or the like. It is widely known to add an inhibitor into the 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 side 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 by friction with a packaged object such as an electronic component due to vibration during transportation, and the electronic component contains carbon black. There was a potential problem of being contaminated with a conductive resin.

This problem is becoming apparent in the form of the occurrence of electrical failure due to the recent miniaturization and higher density of electronic components. Japanese Patent Application No. 2003-271289 discloses a laminate using a polymer type antistatic agent as a countermeasure. A sheet has been proposed. The laminated sheet proposed in Japanese Patent Application No. 2003-271289 solves the above-mentioned rigidity problem, but when a polymer type antistatic agent is blended with a polypropylene resin, the sheet obtained at the time of film formation However, there are problems in that the secondary formability is reduced, and in order to obtain antistatic performance, it is necessary to add a large amount of a polymer type antistatic agent, which is expensive.
Japanese Patent Publication No. 05-8097

  The present invention relates to a composite sheet having excellent rigidity and durability, sufficient antistatic effect, excellent wear resistance and heat resistance, and particularly excellent contents protection as a packaging for electronic parts, and the like The present invention relates to a molded body such as a container formed by secondary molding.

  As a result of earnestly examining the means for solving the above problems, the present inventors have formulated a polymer-type antistatic agent into a polypropylene resin and a polyethylene resin as a skin layer, so that the sheet obtained at the time of film formation can be obtained. Excellent processability at the time of secondary molding, antistatic performance is not deteriorated even by rinsing or wiping, sufficient antistatic effect can be obtained over a long period of time, and moreover, it has a multilayer structure from the viewpoint of economy and rigidity. The present invention has been completed by providing a polyolefin resin layer having excellent rigidity in which a specific amount of filler is blended as a material layer.

That is, according to the first aspect of the present invention, at least one surface of a base material layer containing 20 to 50 parts by mass of a filler in a polyolefin resin, 98 to 50 parts by mass of a polypropylene resin and 2 to 2 parts of a polyethylene resin. It is a composite sheet having a skin layer formed by blending only 50% by weight of an antistatic agent selected from polymer type antistatic agents and having the following requirements (1) and (2): .
(1) The ratio of the thickness of the skin layer to the total thickness of the composite sheet is 2 to 15%.
(2) The surface resistivity of the outer surface of the skin layer is less than 10 ¹² Ω.

  The second invention is a polyolefin-based resin containing at least one side of a base material layer containing 20-50 parts by mass of a filler, a polypropylene-based resin, a polymer antistatic agent, and a total of 100 parts by mass of the resin. It is a composite sheet which has the skin layer formed by mix | blending 0.5-8 mass parts surfactant-type antistatic agent with respect to said, and has the requirements of said (1) and (2).

  In a third aspect of the invention, at least one surface of a base material layer containing 20-50 parts by mass of a filler in a polyolefin-based resin is high in 98-50 parts by mass of a polypropylene resin and 2-50 parts by mass of a polyethylene resin. It has a skin layer formed by blending a molecular type antistatic agent and 0.5 to 8 parts by mass of a surfactant type antistatic agent with respect to a total of 100 parts by mass of the resin component. This is a composite sheet having the requirement 2).

  The package (container) obtained by subjecting the composite sheet of the present invention to secondary molding such as vacuum molding has stable surface antistatic properties over a long period of time, and is excellent in rigidity and wear resistance. In particular, it can be suitably used as a packaging container for electronic components.

  Hereinafter, the present invention will be described in detail.

  The polyolefin-based resin used for the base material layer in the present invention refers to a resin mainly composed of at least one selected from a polyethylene-based resin and a polypropylene-based resin. They are 50 mass% and polypropylene resin 80-50 mass%.

  The polypropylene resin used in the present invention 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. . As the copolymer having propylene as a main component, 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 used in the present invention is an ethylene homopolymer or a copolymer containing ethylene as a main component, and these commercially available resins can be used alone or in combination. is there. Specific examples include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE). Examples of the component copolymer include ethylene-ethyl acrylate resin, ethylene-vinyl acetate copolymer, ethylene-α-olefin copolymer, and the α-olefin includes propylene, 1-butene, 1-pentene, 4 -Methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and the like.

  As the filler used in the present invention, various inorganic fillers and the like can be used, but at least one selected from talc, mica, and glass fiber is preferably used, and talc is particularly preferable. The average particle size of talc is preferably in the range of 10 to 30 μm. If the average particle size of talc is less than 10 μm, the dispersibility of talc may be reduced during extrusion molding of the sheet. If it exceeds 30 μm, pinholes will be generated during film formation of the sheet or when the sheet is secondarily formed into a packaging container. It becomes easy.

The polymeric antistatic agent used in the present invention 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 thereof is 1000 or more. It is common.
Examples of polymer type antistatic agents include polyether ester amide, block copolymer of polyolefin and polyether, graft polymer consisting of polyamide as the backbone polymer, block polymer of polyalkylene ether and polyester as the 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, a block copolymer of polyolefin and polyether is particularly preferable because a sufficient antistatic effect can be obtained with a small amount of addition compared to other polymer type antistatic agents.

  On the other hand, in the present invention, the polymer-type antistatic agent and the surfactant-type antistatic agent can be used in combination. The surfactant type antistatic agent is not particularly limited, and cationic, anionic and amphoteric ionic surfactants and nonionic surfactants can be used, but in order to obtain a sufficient surface resistance value. It is preferable to use an ionic surfactant. Moreover, in an ionic surfactant, since cationic property and amphoteric property are scarce in heat resistance, it is preferable to use it with an anionic surfactant.

  The skin layer of the present invention is formed on at least one surface of the base material layer as described above. In the first invention, the polymer type antistatic agent is composed of 98 to 50 parts by mass of polypropylene resin and 2 to 50 parts by mass of polyethylene resin. In the second invention, a surfactant type of 0.5 to 8 parts by mass with respect to a total of 100 parts by mass of a polymer type antistatic agent and a resin component Resin composition obtained by blending antistatic agent, in the third invention, 98 to 50 parts by mass of polypropylene resin, 2 to 50 parts by mass of polyethylene resin and 100 mass in total of polymer type antistatic agent and resin content A resin composition obtained by blending 0.5 to 8 parts by mass of a surfactant-type antistatic agent with respect to parts is used.

  In the first invention, the polyethylene-based resin has an effect of improving processability when the sheet is secondarily formed into a packaging container, and if the amount is less than 2 parts by mass, the effect cannot be sufficiently obtained, and 50 parts by mass is obtained. If exceeded, the mechanical properties such as rigidity of the sheet will be impaired. In the second invention, the reason why the polyethylene resin is not essential is that the same effect can be obtained by using a polymer resin and a surfactant type antistatic agent in combination with the polypropylene resin. The third invention is a combination of the requirements of both the first and second inventions.

  The amount of the polymeric antistatic agent added to the skin layer varies depending on the type, but when the main component is a block copolymer of polyolefin and polyether, the total amount of polypropylene resin and polyethylene resin is 100. 10-30 mass parts is preferable. If the amount is less than 10 parts by mass, a sufficient surface resistivity cannot be obtained, and if it exceeds 30 parts by mass, it may cause a poor appearance of the sheet and the molded product.

  When a surfactant-type antistatic agent is used in combination with the skin layer (second and third inventions), the addition amount of the surfactant-type antistatic agent is based on a total amount of 100 of the polypropylene resin and the polyethylene resin. It is 0.5-8 mass parts, Preferably it is 0.5-5 mass parts. By using a surfactant type antistatic agent in combination with a polymer type antistatic agent, it becomes possible to obtain a more stable surface resistivity. However, if the addition amount is less than 0.5 parts by mass, the effect is sufficiently obtained. However, if it exceeds 8 parts by mass, the humidity dependency of the surface resistivity becomes high.

The surface resistivity of the laminated sheet of the present invention is less than 10 ¹² Omega. When the surface resistivity is 10 ¹² Ω or more, the sheet itself is easily charged and cannot be suitably used for electronic components and the like that are easily affected by static electricity.

  For the skin layer, processing aids such as antioxidants, UV absorbers, light stabilizers, plasticizers, lubricants, etc., as long as they do not impair the physical properties of the sheet, film-forming properties, and secondary moldability to packaging containers. An agent, a compatibilizer, a colorant, a foaming agent and the like can be added as necessary.

  The addition amount of the filler to the base material layer is 20 to 50 parts by mass, preferably 25 to 40 parts by mass with respect to the polyolefin resin 100. By setting the addition amount of the filler within this range, the rigidity of the sheet is improved and the protection of the contents can be improved.

  The base material layer is processed with various stabilizers such as antioxidants, ultraviolet absorbers, and light stabilizers, plasticizers, lubricants, etc., as long as the physical properties of the sheet, film-forming properties and secondary moldability to packaging containers are not impaired. Auxiliaries, colorants, foaming agents and the like can be added as necessary.

  The thickness of the composite sheet of the present invention is not particularly limited, but a sheet of 100 μm to 2000 μm is preferably used, and more preferably 300 μm to 1500 μm. Moreover, the ratio of the skin layer to the whole composite sheet is 2 to 15% on each side. 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.

  In order to manufacture the composite 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 a generally used mixer such as a tumbler is used. Dry blending is performed, or all or part of the components are kneaded by 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 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. It is possible to laminate other layers on the preformed sheet base layer by a method such as extrusion coating. However, in order to manufacture at a lower cost, a multi-layer die using a multi-manifold die or feed block can be used. It is preferable to obtain a laminated sheet collectively by an extrusion method.

  A secondary-shaped electronic component packaging container can be obtained from the above-mentioned sheet by secondary forming by a known sheet forming method such as vacuum forming, pressure forming, or press forming.

The Example and comparative example of this invention are shown. In these 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 Measured in a 23 ° C. × 20% RH environment and a 23 ° C. × 50% RH environment in accordance with JIS K 6911. For long-term stability, the same measurement was performed after standing for 6 months in an environment of 23 ° C. × 50% RH.

(4) Sheet film-forming sheet: A sheet that is likely to cause adhesion to the cooling roll during film formation was evaluated as x, and a sheet that did not occur was evaluated as ◯.
(5) Secondary moldability In secondary molding using a single vacuum molding machine manufactured by Asano Laboratories, the draw down was large and difficult to mold, and x was easy.
(5) Surface resistivity of molded product Using a single vacuum forming machine 1.0 mm thick sheet manufactured by Asano Laboratories, Inc., molded round cup containers with a draw ratio of 0.2, 0.5, 1.0, The bottom wall thickness and surface resistivity were measured.
(6) Surface state of molded product The appearance of the molded product having the above-mentioned draw ratio of 1.0 was observed, and “X” was given when the antistatic agent was sticky due to bleeding out, and “◯” was given when there was no stickiness.

(Examples 1-4)
After blending the base layer resin and skin layer resin with a tumbler at the composition ratio shown in Table 1, one φ65 mm extruder (L / D = 32), two φ40 mm extruders (L / D = 26) and 600 mm A sheet having a thickness of 1 mm was obtained with a layer constitution ratio shown in Table 1 by a FB block method using a T-die having a width.

(Comparative Examples 1-6)
A sheet having a thickness of 1 mm was obtained in the same manner as in Example except that the composition ratio was as shown in Table 2. A sheet having a thickness of 1 mm was obtained in the same manner as in Example 1 except for the following, with the layer constitution ratio shown in Table 1.

Table 3 shows the evaluation results of each example and comparative example.

Claims (5)

On at least one side of the base material layer containing 20 to 50 parts by mass of talc with respect to a total of 100 parts by mass of the resin component comprising 80 to 50% by weight of polypropylene resin and 20 to 50% by weight of polyethylene resin , It has a skin layer formed by blending only 98 to 50 parts by mass of polypropylene resin and 2 to 50 parts by mass of polyethylene resin with an antistatic agent selected from polymer type antistatic agents. ) And (2), a composite sheet for packaging electronic parts .
(1) The ratio of the thickness of the skin layer to the total thickness of the composite sheet is 2 to 15%.
(2) The surface resistivity of the outer surface of the skin layer is less than 10 ¹² Ω. On at least one side of the base material layer containing 20 to 50 parts by mass of talc with respect to a total of 100 parts by mass of the resin component comprising 80 to 50% by weight of polypropylene resin and 20 to 50% by weight of polyethylene resin , Surfactant type charge of 0.5 to 8 parts by mass with respect to a total of 100 parts by mass of the polymer type antistatic agent and the polymer type antistatic agent in 98 to 50 parts by mass of the polypropylene resin and 2 to 50 parts by mass of the polyethylene resin. A composite sheet for packaging electronic parts , having a skin layer formed by blending an inhibitor and having the following requirements (1) and (2).
(1) The ratio of the thickness of the skin layer to the total thickness of the composite sheet is 2 to 15%.
(2) The surface resistivity of the outer surface of the skin layer is less than 10 ¹² Ω. The composite sheet for packaging electronic parts according to claim 1 or 2, wherein the polymer type antistatic agent contains a block polymer of polyolefin and polyether as main components. The composite sheet for packaging electronic parts according to claim 2 or 3 , wherein the surfactant type antistatic agent is at least one selected from a nonionic type and an anionic type. The molded object for electronic component packaging which consists of a composite sheet of any one of Claims 1-4 .