CN108454206B

CN108454206B - Multilayer sheet made of thermoplastic resin and corrugated board structure made of thermoplastic resin

Info

Publication number: CN108454206B
Application number: CN201710087084.0A
Authority: CN
Inventors: 寺嶋圣二
Original assignee: Sumika Plastech Co Ltd
Current assignee: Sumika Plastech Co Ltd
Priority date: 2017-02-17
Filing date: 2017-02-17
Publication date: 2021-04-06
Anticipated expiration: 2037-02-17
Also published as: CN108454206A

Abstract

The present invention relates to a thermoplastic resin multilayer sheet, wherein a first resin layer is formed of a thermoplastic resin composition containing conductive carbon at a concentration of 13 wt% or more and 20 wt% or less, and a second resin layer formed of a thermoplastic resin composition containing a polymer type antistatic agent is laminated on at least one of 2 plane portions of the first resin layer.

Description

Multilayer sheet made of thermoplastic resin and corrugated board structure made of thermoplastic resin

Technical area

The present invention relates to a thermoplastic resin multilayer sheet and a thermoplastic resin corrugated cardboard (segment ボール) structure, which are used for manufacturing home electric appliances, electric/electronic/motor parts, and office automation equipment parts, are most suitable for long-term use, can prevent electrostatic discharge, and can maintain stable electrostatic diffusibility against humidity changes.

Background

In a manufacturing site of a semiconductor circuit substrate, a liquid crystal panel, a plasma panel, or the like, generation of static electricity is a cause of generation of defective products and engineering failures. However, in these manufacturing sites, friction, peeling, and the like of parts, articles, and the like are frequently repeated in operation in various cases. Therefore, static electricity is generated at a high frequency and a high charge amount even in a clean room. Among them, insulators such as plastics are easily charged because static electricity cannot be diffused. Therefore, plastic button members such as switches, keyboards, and mice, sliding members such as tires, and plastic members such as lever members are very likely to generate static electricity and have a large amount of charged electricity due to repeated contact such as friction and peeling during operation, and thus are receiving attention.

In the production of articles made of plastics used for home electric appliances, electric and electronic motor parts, and the like, thermoplastic resins such as polyolefin resins, polyvinyl chloride resins, and synthetic rubbers are used as main raw materials. Such plastic articles are electrically insulating and very easily charged with static electricity, and it is necessary to take measures against static electricity.

As a countermeasure against static electricity, there is a method of adding a conductive agent or an antistatic agent to a thermoplastic resin used for plastic articles to impart static electricity diffusibility.

Here, conductive carbon is generally used as the conductive agent, and low-molecular antistatic agents and high-molecular antistatic agents are generally used as the antistatic agents.

Methods of filling carbon black in a thermoplastic resin are known (Japanese unexamined patent publication Nos. 60-65064 and 55-31103), but when carbon black is mixed in a thermoplastic resin, the carbon black is scattered and the working environment is deteriorated. In addition, the shear heat generated when carbon black is mixed causes a decrease in the molecular weight of the thermoplastic resin. Therefore, in order to disperse carbon black in a thermoplastic resin, first, a master batch of a thermoplastic resin containing carbon black at a high concentration is produced, and thereafter, the master batch is mixed into the thermoplastic resin.

Examples of the low-molecular antistatic agent include monoglyceride, sodium alkylbenzenesulfonate and the like, but such a low-molecular antistatic agent is easy to bleed out because of its small molecular weight. Therefore, it is not suitable as an antistatic agent for use around electronic parts. Further, low-molecular antistatic agents have inferior durability of antistatic performance and high humidity dependency compared with conductive carbon and high-molecular antistatic agents.

Patent document 1 describes a resin composition in which polyphenylene sulfide is mixed with conductive carbon black, natural graphite flakes and an inorganic filler.

Patent document 2 describes a resin composition in which a polyphenylene sulfide resin is mixed with conductive carbon black, graphite, and a filler.

Patent document 3 describes a resin composition in which conductive carbon black and artificial graphite are mixed with a thermoplastic resin.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent application laid-open No. Sho 62-172059 (published 29/7 in 1987)

[ patent document 2] Japanese patent application laid-open No. Hei 1-272665 (published 10/31/1989)

[ patent document 3] Japanese patent application laid-open No. Hei 7-286103 (published 10/31/1995)

Disclosure of Invention

[ problem to be solved by the invention ]

However, according to the techniques described in patent documents 1 to 3, when a thermoplastic resin sheet is formed by mixing conductive carbon such as carbon black, it is difficult to control the electrostatic diffusibility of the thermoplastic resin sheet. This is because, in order to impart electrostatic diffusibility to a thermoplastic resin, it is necessary to form a three-dimensional mesh structure from conductive carbon such as carbon black, and appropriately connect the mesh structures to form a conductive path bridging electrodes to control conductivity, and it is difficult to uniformly disperse the conductive carbon in the thermoplastic resin at a concentration of not more than the percolation threshold.

Here, the percolation threshold refers to the concentration of conductive carbon at the inflection point where the resistance of the thermoplastic resin changes greatly. When the concentration of the conductive carbon is less than or equal to the percolation threshold, the conductive carbon is likely to be unevenly dispersed when kneaded by a molding machine. Therefore, in a densely formed portion of the three-dimensional mesh structure made of conductive carbon, the surface resistance value of the thermoplastic resin containing the conductive carbon may show a value of a conductive region higher in conductivity than the electrostatic diffusion region.

Further, for example, when a thermoplastic resin sheet is formed by mixing a thermoplastic resin with a master batch containing conductive carbon, the concentration of the conductive carbon may be locally higher than the percolation threshold. At this time, the surface resistance value of the thermoplastic resin containing conductive carbon shows a value of the conductive region higher than the conductivity of the electrostatic diffusion region.

In this way, when the surface resistance value of the thermoplastic resin containing conductive carbon indicates the value of the conductive region, for example, when the substrate on which static electricity is accumulated comes into contact with a portion indicating the surface resistance value of the conductive region, a large discharge occurs. Such discharge is a cause of a serious failure such as damage to an IC, a transistor, a circuit board, or the like, which is vulnerable to static electricity.

When the thermoplastic resin is mixed with conductive carbon at a concentration of the percolation threshold or higher, the conductive carbon-containing thermoplastic resin composition exhibits a surface resistance value of the conductive region. Therefore, when the substrate on which static electricity is accumulated is brought into contact with the substrate, a large discharge occurs.

The present invention has been made in view of the above problems, and an object thereof is to provide a thermoplastic resin multilayer sheet capable of preventing electrostatic discharge.

[ means for solving the problems ]

The present inventors have made diligent studies to solve the above-described technical problems, and finally have achieved the present invention as described below.

The multilayer sheet made of thermoplastic resin according to one embodiment of the present invention is characterized in that the first resin layer is formed of a thermoplastic resin composition containing conductive carbon at a concentration in a range of 13 wt% to 30 wt%, and the second resin layer formed of a thermoplastic resin composition containing a polymer type antistatic agent is laminated on at least one of 2 planar portions of the first resin layer.

[ Effect of the invention ]

According to the present invention, there is provided a thermoplastic resin multilayer sheet capable of preventing electrostatic discharge.

Drawings

FIG. 1 is a view schematically illustrating an embodiment of a thermoplastic-resin multilayer sheet according to the present invention and a modification thereof.

[ description of reference numerals ]

10 Plastic corrugated cardboard (corrugated cardboard structure made of thermoplastic resin)

11 Plastic corrugated cardboard (corrugated cardboard structure made of thermoplastic resin)

12 Plastic corrugated cardboard (corrugated cardboard structure made of thermoplastic resin)

20 part of lining material (Flat plate part)

21 first layer (Flat plate part, second resin layer)

22 second layer (Flat part, first resin layer)

30 rib part (connecting part, first resin layer)

31 Rib part (connecting part, first resin layer)

32 Rib section (Joint, first resin layer)

Detailed Description

< multilayer sheet made of thermoplastic resin >

The multilayer sheet made of thermoplastic resin according to one embodiment of the present invention includes a first resin layer made of a thermoplastic resin composition containing conductive carbon at a concentration in a range of 13 wt% to 30 wt%, and a second resin layer made of a thermoplastic resin composition containing a polymer type antistatic agent is laminated on a planar portion on the first resin layer side.

For example, when a sheet made of a thermoplastic resin is extrusion-molded in a continuous batch manner, regenerated particles (リペレット) obtained from the end of the extrusion-molded sheet and a master batch containing conductive carbon may be mixed with a virgin resin and reused. In this case, when the thermoplastic resin sheet to be produced contains conductive carbon at a concentration of the percolation threshold or less, the concentration of the conductive carbon tends to be uneven when kneaded by the molding machine. Therefore, it is difficult to form the thermoplastic resin sheet so that the surface resistance value of the entire surface shows a value of an electrostatic diffusion region described later.

However, according to the thermoplastic resin multilayer sheet of the present embodiment, even if there is a portion having the surface resistance value of the conductive region in the first resin layer, the second resin layer laminated on the first resin layer can prevent static electricity from being discharged to the portion exhibiting the surface resistance value of the conductive region. In addition, even if the content of the conductive carbon in the first resin layer is such an amount that the surface resistance value of the first resin layer shows a value of the conductive region, it is possible to prevent static electricity from being discharged to the first resin layer. That is, the multilayer sheet made of thermoplastic resin according to the present embodiment can prevent static electricity discharge stably while avoiding excessive control of the dispersibility and concentration of conductive carbon during production.

In addition, in the case of an article in which a polymer type antistatic agent is added to a thermoplastic resin, the surface resistance value of the article changes greatly with a change in humidity. For example, when the thermoplastic resin containing a polymer type antistatic agent is left in a low humidity environment in winter, the surface resistance value of the thermoplastic resin becomes high. More specifically, the surface resistance value of the thermoplastic resin containing the polymeric antistatic agent shows a value exceeding the antistatic region of the static electricity diffusing region. Therefore, static electricity cannot be slowly dissipated, and a product made of a thermoplastic resin containing a polymer type antistatic agent is easily charged. Therefore, for example, there is a problem that discharge electricity occurs when the article comes into contact with an uncharged substrate while the article is charged.

However, in the multilayer sheet made of thermoplastic resin according to the present embodiment, the first resin layer containing conductive carbon and the second resin layer containing a polymer type antistatic agent are laminated, whereby a surface resistance value stable with respect to humidity can be maintained. Therefore, for example, even when used in an environment with high humidity such as outside of a clean room, static electricity generated when the second resin layer is rubbed or peeled can be diffused in the first resin layer and the second resin layer.

Therefore, the thermoplastic resin multilayer sheet according to the present embodiment can be suitably used as a member that is easily charged by repeated operations of an operator, such as an article in a clean room (a platen and a frame plate of a table and a partition plate for partitioning a work area). Further, since the static electricity generated in the clean room can be appropriately attenuated, contamination in the clean room can be reduced. In addition, electrostatic discharge in a clean room or other work place can be prevented without depending on whether humidity management is performed or not.

Generally, the surface resistance value of an article formed of a thermoplastic resin varies depending on the kind, amount, and the like of a conductive agent and an antistatic agent to be mixed. Here, the thermoplastic resin is classified into the following (1) to (3) depending on the range of the surface resistance value.

(1) A conductive resin composition having a molecular weight of less than 1X 10⁵Omega surface resistance value of the resin composition. The conductive resin composition has high conductivity (low resistance value), and can be used as a conductive material for a charged objectThe composition can cause severe electrostatic discharge when contacted. In the present specification, the surface resistance value of the conductive region is less than 1 × 10⁵Surface resistance values in the range of Ω.

(2) A static dissipative (static dissipative) resin composition having a molecular weight of 1X 10⁵Omega is more than or equal to 1 multiplied by 10⁹Omega surface resistance value of the resin composition. The static electricity diffusing resin composition not only exhibits conductivity to quickly dissipate its electrification but also can prevent a severe static discharge when a charged object comes into contact with the thermoplastic resin. The electrostatic diffusible resin composition does not have conductivity to such an extent that it can shield an electrostatic field.

(3) An antistatic (antistatic) resin composition having a molecular weight of 1X 10⁹Omega is more than or equal to 1 multiplied by 10¹⁴Omega surface resistance value of the resin composition. Although it has conductivity to prevent self-charging to some extent, it does not have conductivity to the extent that static electricity of a charged object can be rapidly diffused. In the present specification, the surface resistance value of the antistatic region means 1 × 10⁹Omega is more than or equal to 1 multiplied by 10¹⁴Surface resistance value of Ω.

Of the resin compositions having 3 kinds of electrical characteristics, 1X 10 set according to the surface resistance value and the like in IEC (International electrotechnical Commission) 61340-5-1/5-2 was satisfied⁵Omega is more than or equal to 1 multiplied by 10⁹An electrostatic diffusible resin composition having a surface resistance value in the range of Ω is preferable. In the case of this electrostatic diffusible resin composition, it is possible to prevent discharge of static electricity from a charged object and also prevent the electrostatic diffusible resin composition itself from being charged. Therefore, the second resin layer is formed of the electrostatic diffusible grease composition. In the present specification, the surface resistance value of the electrostatic diffusion region means 1 × 10⁵Omega is more than or equal to 1 multiplied by 10⁹Surface resistance values in the range of Ω. The first resin layer may be formed of a conductive resin composition or an electrostatic diffusible resin composition, and is more preferably formed of a conductive resin composition. This is because if the first resin layer is composed of a conductive resin, the first resin layer is composed of a conductive resinThe formation of the substance can diffuse static electricity more rapidly.

[ first resin layer ]

The first resin layer is formed from a thermoplastic resin composition containing conductive carbon at a concentration in the range of 13 wt% to 30 wt%.

The thickness of the first resin layer is not particularly limited, but is preferably in the range of 10 μm to 2000 μm.

(thermoplastic resin)

Examples of the thermoplastic resin include polyolefin resins, polyvinyl chloride resins (PVC), polystyrene resins, and the like, and polyolefin resins are more preferable.

Examples of the polyolefin resin include polyethylene resins and polypropylene resins, and these resins may be used in combination. Examples of the polyethylene resin include low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene. Examples of the polypropylene resin include a propylene homopolymer, a copolymer of propylene and a small amount of a comonomer such as ethylene and/or α -olefin, and a polymer in which an amorphous ethylene/α -olefin copolymer is dispersed. In particular, polypropylene-based resins are preferred from the viewpoint of rigidity or heat resistance.

(conductive carbon)

Examples of the conductive carbon include carbon black, carbon fibrils (フィブリル) typified by carbon nanotubes, carbon nanofibers (ナノファイバー), and graphite.

By mixing conductive carbon into the thermoplastic resin, the surface resistance value can be adjusted to the value of the conductive region at a lower cost than in the case where the conductivity of the thermoplastic resin is controlled using a metal.

In addition, carbon black, carbon nanotubes, or carbon nanofibers are more preferably used for the conductive carbon, and carbon black is more preferably used from the viewpoint of cost.

The carbon black preferably has a Dibutyl Phthalate (DPB) oil absorption of 250ml/100g or more, more preferably 300ml/100g or moreMore preferably 350ml/100g or more of carbon black. The DPB oil absorption referred to herein means a value measured by the method specified in ASTM D2414. Further, the carbon black preferably has a BET surface area of 200cm²More than g, further 400cm²More preferably,/g or more. Examples of commercially available carbon blacks include ketjen black EC and ketjen black EC-600JD, which are ketjen black international (ケッチェンブラックインターナショナル).

Examples of the carbon nanotube include carbon-based fibers having a hollow structure and less branching, which have a fiber diameter of less than 75nm and are described in, for example, U.S. Pat. No. 4663230, U.S. Pat. No. 4663230, U.S. Pat. No. 5165909, U.S. Pat. No. 5171560, U.S. Pat. No. 5578543, U.S. Pat. No. 5589152, U.S. Pat. No. 5650370, and U.S. Pat. No. 6235674. The carbon nanotubes also include a curled shape that is twisted once at a pitch of 1 μm or less. Examples of commercially available carbon nanotubes include HYPERION available from HYPERIONCATALYSIS (ハイペリオンキャタリスト).

Examples of the carbon nanofibers include carbon fibers having a hollow structure and a large number of branched structures, the carbon fibers having a fiber diameter of 75nm or more. Examples of commercially available carbon nanofibers include VGCF and VGNF available from showa electric corporation.

Examples of the graphite include those obtained by heating smokeless carbon, pitch, and the like at a high temperature in an electric arc furnace, and those produced naturally. Further, like carbon black, graphite is also a conductive agent which can produce the first resin layer at low cost.

The concentration of the conductive carbon in the thermoplastic resin may be appropriately adjusted depending on the type of the conductive carbon, the conductivity, and the like. For example, when the total of the thermoplastic resin and the conductive carbon is 100 wt%, the concentration may be in the range of 13 wt% to 30 wt%, and more preferably in the range of 15 wt% to 20 wt%. When the concentration of the conductive carbon is in the range of 13 wt% or more and 30 wt% or less, the thermoplastic resin composition can have a surface resistance value of the conductive region or the static electricity diffusing region, and can be obtained.

(other compositions)

The thermoplastic resin used in the present embodiment may contain various additives such as fillers such as silica, mica, and talc, reinforcing materials such as glass fibers, aramid fibers, and ultra-high molecular weight polyethylene fibers, heat stabilizers, ultraviolet absorbers, ultraviolet stabilizers, and coloring agents, as needed, as long as the moldability and the electrical conductivity and mechanical strength of the multilayer sheet made of the thermoplastic resin are not affected.

[ second resin layer ]

The second resin layer is formed of a thermoplastic resin composition containing a polymeric antistatic agent. The second resin layer may contain various additives such as a filler, a reinforcing material, a heat stabilizer, an ultraviolet absorber, an ultraviolet stabilizer, and a colorant, as in the first resin layer.

The second resin layer is laminated so as to cover one surface of the first resin layer. Therefore, the second resin layer also covers a portion of the first resin layer where the surface resistance value locally appears as the surface resistance value of the conductive region. Therefore, discharge of static electricity charged to the component or the like by the first resin layer can be prevented.

In addition, the second resin layer covers one surface of the first resin layer, and thus, the conductive carbon contained in the first resin layer can be prevented from being released from the one surface. Therefore, contamination of the working environment by the detached conductive carbon can be prevented. Further, since the second resin layer does not contain a black pigment such as conductive carbon, a molded article having a desired color can be obtained by adding a pigment.

The thermoplastic resin of the second resin layer may be the same as the above-described thermoplastic resin. In the thermoplastic resin multilayer sheet, the thermoplastic resin used for the second resin layer and the thermoplastic resin used for the first resin layer may be different thermoplastic resins. However, in order to prevent warpage due to a difference in thermal expansion coefficient after moldability and to improve adhesion between the first resin layer and the second resin layer, it is more preferable to use the same thermoplastic resin.

The thickness of the second resin layer is not particularly limited, but the thickness of the second resin layer may be in the range of 5 μm to 100 μm. Since the second resin layer is laminated so as to be closely adhered to the first resin layer, static electricity generated in the second resin layer can be conducted to the first resin layer. Therefore, the second resin layer is not excessively thick, and static electricity generated in the thermoplastic resin multilayer sheet can be diffused. Therefore, the amount of the polymeric antistatic agent used can be reduced, and the cost of the thermoplastic resin multilayer sheet can be reduced.

The method for producing the thermoplastic-resin-made multilayer sheet according to the present embodiment is not particularly limited, and may be produced by laminating a charge damping layer and a conductive resin layer by a known molding technique or a known bonding technique to form a multilayer structure. However, the extrusion molding method is preferable from the viewpoint of productivity, and the production is more preferably performed by a known multilayer coextrusion method using a multilayer die.

(Polymer type antistatic agent)

As the polymer type antistatic agent, known ones can be used, and for example, a block copolymer composed of a hydrophobic segment and a hydrophilic segment can be used. The block copolymer as a high molecular type antistatic agent is formed by ester bond, ether bond, amide bond, imide bond, urethane bond, urea bond, or the like between a hydrophobic segment and a hydrophilic segment.

Examples of the hydrophobic segment include polyolefin segments, and examples of the polyolefin segment include segments composed of polyethylene, polypropylene, and an ethylene-propylene copolymer. Here, the polyolefin segment may also be fluorine-modified. The hydrophobic segment may be hydrophobic, and examples thereof include hydrophobic amines, hydrophobic esters, hydrophobic amides, hydrophobic imides, and hydrophobic ester-amides having a hydrophobic group such as an alkylene group or an aromatic group. The hydrophobic segment may have a hydrophobic side chain such as an alkyl group.

The hydrophobic segment such as a polyolefin segment has polar groups such as carbonyl groups, hydroxyl groups, and amino groups at both ends thereof. The block copolymer composed of the hydrophobic segment and the hydrophilic segment can be obtained by polymerizing the polar groups at both ends of the hydrophobic segment onto the carbonyl group, hydroxyl group, amino group, and the like present at both ends of the hydrophilic segment, or by crosslinking with diisocyanate, diglycidyl ether, and the like.

Examples of the hydrophilic segment include a polyether segment, a polyether-containing hydrophilic polymer segment, a cationic polymer segment, and an anionic polymer segment. The polyether segment is typically a polyether diol, and examples thereof include polyethylene glycol, polypropylene glycol, and a copolymer of ethylene glycol and propylene glycol. The hydrophilic polymer segment containing polyether has a polyether segment, and examples thereof include polyether diamine, polyether ester amide, polyether amide imide, polyether ester, polyether amide, and ether urethane. The polyether segment and the polyether segment may be linear or branched. Further, the cationic polymer segment may be separated from BF at intervals between nonionic molecular chains₄ ^-、PF₆ ^-、BF₃Cl^-And PF₅Cl^-And cationic polymer segments formed by forming counter ions of quaternary ammonium salt or phosphonium salt with super acidic anions. Examples of the anionic polymer segment include polymer segments obtained by copolymerizing an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid having sulfonyl groups, which is a salt of only sulfonyl groups, with a diol or a polyether. Such polymer antistatic agents are described in detail in, for example, Japanese patent laid-open Nos. 2001-278985, 2003-048990 and 2012-031395.

Among the high molecular type antistatic agents exhibiting the structure as described above, for example, a polyolefin-polyether block copolymer, a polyetheresteramide as a block copolymer of a polyether and a hydrophobic esteramide, a polyetheramide as a block copolymer of a polyether and a hydrophobic amide, or a polyetheramideimide as a block copolymer of a polyether and a hydrophobic amideimide may be more preferably used, or a polyethylene glycol (meth) acrylate copolymer may be more preferably used. In addition, for example, when a polypropylene resin is used as the thermoplastic resin, it is preferable to use a block copolymer having a structure in which segments of a polyolefin portion and a hydrophilic polymer portion described in jp 2008-274031 a are repeatedly and alternately bonded, as an example of a polypropylene-polyether block copolymer, for the high-molecular antistatic agent, from the viewpoint of compatibility.

In addition, in order to further improve the antistatic property of the polymeric antistatic agent, an alkali metal or alkaline earth metal salt, a quaternary ammonium salt, a surfactant, an ionic liquid, or the like may be mixed in a range not affecting the effect of the present invention.

The commercially available product of polyetheresteramide includes TPAE manufactured by fuji chemical industries co. Commercially available polypropylene-polyether block copolymers include PELESTAT (ペレスタット)300, PELESTAT230, and PELECTRON (ペレクトロン) PVL, all available from Sanyo chemical industries, Ltd.

By using at least 1 of these polymer type antistatic agents, the electrostatic diffusibility in the second resin layer can be suitably maintained.

The content of the polymer type antistatic agent may be appropriately adjusted depending on the kind of the thermoplastic resin, the polymer type antistatic agent, and the shape of the thermoplastic resin multilayer sheet, and is not limited. However, when the total amount of the thermoplastic resin and the polymeric antistatic agent is 100% by weight, the amount is preferably in the range of 10% by weight or more and 60% by weight or less, and more preferably in the range of 10% by weight or more and 50% by weight or less. When the concentration of the polymer type antistatic agent in the second resin layer is 10% by weight or more, a multilayer sheet made of thermoplastic resin exhibiting a surface resistance value of the electrostatic diffusion region can be obtained when the multilayer sheet is laminated on the first resin layer. When the concentration of the polymer type antistatic agent is 60% by weight or less, the shape of the thermoplastic resin multilayer sheet can be stably maintained, and appropriate surface smoothness can be obtained.

[ multilayer sheet made of thermoplastic resin according to another embodiment ]

The thermoplastic resin multilayer sheet is not limited to the above-described embodiments. For example, a multilayer sheet made of thermoplastic resin according to another embodiment is a multilayer sheet made of thermoplastic resin in which a second resin layer is laminated on one of 2 planar portions of a first resin layer, and a second resin layer is further laminated on a planar portion of the first resin layer on the opposite side of the planar portion on which the second resin layer is laminated.

According to the above configuration, the 2 plane portions of the first resin layer can be covered with the second resin layer. Therefore, the charging member can be prevented from discharging static electricity on both surfaces of the thermoplastic resin multilayer sheet. In addition, the conductive carbon can be prevented from being detached from both surfaces of the first resin layer.

Further, the multilayer sheet made of thermoplastic resin according to another embodiment has a structure in which 3 kinds of 5 layers, that is, a second resin layer, a first resin layer, a thermoplastic resin layer, another first resin layer, and another second resin layer are laminated in this order. The thermoplastic resin layer is a resin layer containing no polymeric antistatic agent or conductive carbon.

The structure of the thermoplastic resin multilayer sheet is not limited as long as the second resin layer is laminated so that the second resin layer is in close contact with the first resin layer on at least one surface layer thereof.

< Plastic corrugated cardboard >

A plastic corrugated cardboard (a corrugated cardboard structure made of a thermoplastic resin) according to an embodiment of the present invention will be described in detail with reference to fig. 1.

Fig. 1 (a) is a schematic view illustrating a plastic corrugated cardboard 10 according to an embodiment of the present invention. As shown in fig. 1 (a), the gasket (flat plate) 20 and the rib (connecting portion) 30 are provided, and the gasket 20 is composed of a first layer 21 and a second layer 22. Here, 2 first layers 21 are constructed by the second resin layer. In addition, the 2 second layers 22 and the plurality of rib portions 30 are integrally molded by extrusion molding the thermoplastic resin composition forming the first resin layer. That is, the plastic corrugated cardboard 10 is one form of a 2-type 3-layer thermoplastic resin multilayer sheet.

The plurality of rib portions 30 divide 2 planar portions of the 2 second layers 22 facing each other in parallel with a space portion between the 2 planar portions, and bridge 2 opposing planar portions of the 2 planar portions. Thereby, the plastic corrugated cardboard, which can be used as a recyclable box, a building material, and the like having light weight and strength, can be integrally formed. Therefore, the plastic corrugated cardboard can be used for electronic equipment substrates, boxes and cases for carrying parts, and the like, which require solving the electrostatic problem.

[ Plastic corrugated cardboard relating to modification ]

The plastic corrugated cardboard according to the present invention is not limited to the above-described embodiments. For example, as shown in fig. 1 (b), a plastic corrugated cardboard 11 according to a modification has a structure in which a corrugated 1-piece rib portion 31 is provided between second layers 22 of 2 liner portions 20. Here, the rib portions 31 are formed of the first resin layer, as in the second layer 22. In the plastic corrugated cardboard 11, the rib portion 31 and the second layer 22 facing each other may be attached by hot melting to form a bridge or may be attached by using an adhesive having electrostatic diffusibility to form a bridge.

As shown in fig. 1 (c), the plastic corrugated cardboard 12 according to another modification has a structure in which 2 second layers 22 are bridged by 1 rib portion 32 bent obliquely.

In the plastic corrugated cardboard, the shape of the rib portion is not limited as long as it has a reinforcing function by connecting the liner portions, and for example, the rib portion may have a honeycomb structure.

As for the thermoplastic resin contained in the liner portion and the rib portion constituting the plastic corrugated cardboard, among the polyolefin resins, a polypropylene resin or a polyethylene resin is preferable, and particularly, a polypropylene resin is preferable in view of rigidity, heat resistance, and the like.

The content of the polymeric antistatic agent in the thermoplastic resin composition forming the second layer of the liner portion of the plastic corrugated cardboard may be appropriately adjusted depending on the type of the thermoplastic resin, the polymeric antistatic agent, and the shape of the multilayer sheet of the thermoplastic resin, and is not limited. However, when the total amount of the thermoplastic resin and the polymeric antistatic agent is 100% by weight, the amount is preferably in the range of 10% by weight or more and 30% by weight or less, and more preferably in the range of 10% by weight or more and 20% by weight or less. If the concentration of the polymer type antistatic agent in the first layer is 10 wt% or more, a plastic corrugated cardboard in which the second layer exhibits a surface resistance value of an electrostatic diffusion region can be obtained. When the concentration of the polymer type antistatic agent is 30% by weight or less, a plastic corrugated cardboard having a suitable surface smoothness can be obtained.

The grammage (basis weight) (weight per unit area) of the plastic corrugated cardboard, the thicknesses of the liner portion and the rib portion, and the like are not particularly limited and may be selected according to the application. The grammage of the corrugated cardboard structure 1 made of thermoplastic resin is preferably 200g/m²10000g/m above²In the following range, the thicknesses of the lining portion and the rib portion are preferably in the ranges of 1mm to 20mm, respectively. For example, when the plastic corrugated cardboard using polyolefin resin is used for a recyclable box, the grammage thereof is preferably 500 to 2000g/m²The thicknesses of the lining portion and the rib portion are preferably in the ranges of 3mm to 7mm, respectively.

The present invention is not limited to the above embodiments, and various modifications within the scope shown in the claims may be made, and embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present invention.

The present invention will be described in further detail with reference to examples below, but the present invention is not limited to these examples.

[ examples ] A method for producing a compound

< example >

As examples 1 and 2 and comparative examples, sheets were produced from the structure and composition of each layer, and the surface resistance values of the surface layers of these sheets were evaluated for max, min, Δ max-min, and humidity dependence.

[ example 1]

In example 1, 2 kinds of 3-layer (skin layer/core layer/skin layer) thermoplastic resin multilayer sheets were produced. Here, the core layer is a center layer of 2 kinds of 3-layer sheets made of thermoplastic resin, and the surface layer is a layer laminated on both surfaces of the core layer and is referred to as a first resin layer.

(example 1-1)

First, as the multilayer sheet of example 1-1, a multilayer sheet of 2 types and 3 layers was produced, in which the concentration of conductive carbon in the core layer was 16.5 wt%, and the ratio of the polymer type antistatic agent in the surface layer was 20 wt%.

For the conductive carbon in the core layer, commercially available furnace black (carbon black) was used, and for the polymer type antistatic agent in the surface layer, polyethylene (kr) npvl, manufactured by sanyo chemical industries, co. In addition, in the core layer and the skin layer, AS the thermoplastic resin, Noblen (ノーブレン) AS171L (melt flow Rate (MFR): 1.0g/10 min, 230 ℃ C.) manufactured by Sumitomo chemical Co., Ltd., which is a polypropylene-based resin, was used.

First, a master batch of furnace black was produced by mixing furnace black to 30% by weight in a commercially available polypropylene resin without scattering the furnace black. Then, the obtained master batch was melt-mixed with Noblen AS171L so that the concentration of furnace black was 16.5 wt%, thereby obtaining a thermoplastic resin composition forming a core layer.

The thermoplastic resin composition for forming the skin layer was obtained by melt-mixing PELECRON PVL into Noblen AS171L so that the concentration of PELECRON PVL was 20 wt%.

The multilayer sheet of example 1-1 had a size of 100mm × 100mm, and a test piece was produced by using a laminator manufactured by Modern Machinery (モダンマシナリー) and adjusting the drawing speed so that the surface layer thickness of the multilayer sheet made of a thermoplastic resin was 30 μm and the core layer thickness was 100 μm. That is, the thickness ratio of each layer is the surface layer: core layer: surface layer 3: 100: 3.

regarding the processing conditions, the cylinder temperatures in the extruder for the core layer and the extruder for the skin layer were 230 ℃. The extrusion amount of the surface layer extruder is 6kg/h, and the extrusion amount of the core layer extruder is 16 to 17 kg/h. The take-off speed of the surface layer extruder was 4.7m/min, and the take-off speed of the core layer extruder was 4.7 m/min.

(examples 1 to 2)

The multilayer sheet of example 1-2 was produced under the same conditions as in example 1-1, except that the concentration of PELECTRON PVL in the surface layer was adjusted to 50% by weight.

[ example 2]

Hereinafter, as example 2, a plastic corrugated cardboard having a hollow resin structure as shown in fig. 1 (a) was formed.

The composition of the core layer portion (second layer 22 and rib portion 30) was the same as that of the core layer of example 1-1, and the composition of the surface layer portion (first layer) was the same as that of the surface layer of example 1-1.

Plastic corrugated cardboard including a surface layer and a core layer (an inner layer of a liner portion and a rib portion) was manufactured using a first extruder, a second extruder and a multi-layer T-die. For the first extruder, a single-screw extruder (diameter Φ 50mm) was used to extrude the material of the surface layer portion. In addition, as the second extruder, a single-screw extruder (diameter Φ 115mm) was used to extrude the material for the core layer. For the multilayer T-shaped die, a shunt type T-shaped die with an extrusion width of 2000mm is adopted.

The plastic corrugated cardboard is produced by performing multi-layer extrusion molding with the temperatures of the extruder and the multi-layer T-shaped die set to 200 to 230 ℃, the extrusion amounts of the first extruder and the second extruder set to 310kg/h and 22kg/h, respectively, and the drawing speed set to 2.8 m/min.

[ comparative example 1]

Hereinafter, as comparative example 1, a single-layer sheet of a single layer (only the first resin layer) having different concentrations of conductive carbon was produced.

Comparative example 1-1

The single-layer sheet of comparative example 1-1 was prepared under the same conditions as the core layer of example 1-1, except that the furnace black concentration was 5 wt%.

The single-layer sheet of comparative example 1-1 was molded using a laminator manufactured by Modern Machinery under conditions of a cylinder temperature of 230 degrees, an extrusion amount of 16kg/h, and a drawing speed of 4.7m/min to form a sheet having a thickness of 100. mu.m.

Comparative examples 1 and 2

The single-layer sheet of comparative example 1-2 was produced under the same conditions as the sheet of comparative example 1-1, except that the furnace black concentration was adjusted to 10 wt%.

Comparative examples 1 to 3

The single-layer sheet of comparative example 1-3 was produced under the same conditions as the sheet of comparative example 1-1, except that the furnace black concentration was adjusted to 13 wt%.

Comparative examples 1 to 4

The single-layer sheets of comparative examples 1 to 4 were produced under the same conditions as those of comparative example 1 to 1, except that the furnace black concentration was adjusted to 16.5% by weight.

Comparative examples 1 to 5

The single-layer sheets of comparative examples 1 to 5 were produced under the same conditions as those of comparative example 1 to 1, except that the furnace black concentration was adjusted to 20% by weight.

[ comparative example 2]

Hereinafter, as comparative example 2, a multilayer sheet having 2 kinds and 3 layers, in which the surface layer contains a polymer type antistatic agent and the core layer does not contain conductive carbon, was produced.

Comparative example 2-1

In the multilayer sheet of comparative example 2-1, an experiment was conducted under the same conditions as in example 1-1 except that nobileas 171L used in example 1-1 was used alone as a core layer. The results are shown in Table 1.

Comparative examples 2 and 2

The multilayer sheet of comparative example 2-2 was produced under the same conditions as in comparative example 2-1, except that the concentration of PELECTRON PVL was adjusted to 50% by weight.

[ comparative example 3]

Hereinafter, as comparative example 3, a multilayer sheet having 2 kinds of 3 layers, in which the surface layer does not contain a polymer type antistatic agent and the core layer contains conductive carbon, was produced.

The multilayer sheet of comparative example 3 was subjected to the experiment under the same conditions as in example 1-1, except that the surface layer did not contain PELECTRON PVL.

Table 1 shows the production conditions of the examples and comparative examples.

[ TABLE 1]

[ evaluation of surface resistance value ]

Hereinafter, the surface resistance values of the surface layers of the sheets of examples and comparative examples were measured, and max, min, Δ max-min and humidity dependency of the surface resistance values were evaluated.

The surface resistance value was measured under conditions of an applied voltage of 100v and a measurement time of 60 seconds using a surface resistance/volume resistance meter (MODEL:152-1) manufactured by Trek Japan (トレックジャパン) and a CR probe (MODEL:152P-CR) manufactured by Trek Japan, which were capable of measuring the surface resistance according to the ESD Association standards. The surface resistance value at a humidity of 20% was adjusted using an environmental chamber (MODEL5532) of Electro-tech systems (ETS), and 15 points were measured at a temperature of 24.8 ℃. Further, the surface resistance value at a humidity of 60% was adjusted by using a low-temperature constant-humidity machine FX421P manufactured by nakegaku corporation, and 15 points were measured at23 ℃.

The evaluation results are shown in table 2 below. In table 2, max is the maximum value among the surface resistance values measured at 15 points, and min is the minimum value among the surface resistance values measured at 15 points. Δ max-min is the difference between the maximum and minimum values of the surface resistance value at each humidity. In addition, the humidity-dependent difference max-min is the maximum amplitude of the difference between the surface resistance values resulting from the difference in humidity conditions, and is the maximum difference among 4 data of max and min of the surface resistance value at 20% humidity and max and min of the surface resistance value at 60% humidity. In the humidity dependence difference of Table 2, max-min was divided by 10⁵Or 10¹⁰The values obtained are reported in the left column and are divided by 10⁵Or 10¹⁰Which one is described in the right column. For example, by 10⁵When, it is described as "power 5", divided by 10¹⁰In time, it is described as "10 th power".

[ TABLE 2]

As shown in table 2, the multilayer sheets of examples 1-1 and 1-2 exhibited surface resistance values of the electrostatic diffusion regions on the surface layers. Further, the multilayer sheets of examples 1-1 and 1-2 had small fluctuation in surface resistance value with respect to humidity change (humidity-dependent difference). In addition, the plastic corrugated cardboard of example 2 had a cross-sectional shape of a multi-layer hollow board, but the change in surface resistance value with respect to humidity was small in the same manner as in examples 1-1 and 1-2.

On the other hand, the single-layer sheets of comparative examples 1 to 1 and 1 to 2 had a furnace black content of 10 wt% or less, and the surface resistance value thereof showed a value in the antistatic region higher than that in the static electricity diffusing region. In addition, the single-ply sheets of comparative examples 1 to 3 gave results in which the surface resistance value varied greatly with respect to humidity, as compared with the multi-ply sheets of examples 1 to 1 and 1 to 2 and the plastic corrugated cardboard of example 2. The single-layer sheets of comparative examples 1 to 4 having a furnace black content of 20 wt% showed small fluctuation in surface resistance value with respect to humidity change, and showed a value close to the lower limit of the electrostatic diffusion region. However, in the single-layer sheets of comparative examples 1 to 4, if the amount of carbon added varied by a few weight%, the surface resistance value decreased by 1/10 times or more, and became less than 1 × 10⁵And omega conductive regions. Therefore, there is a possibility that a strong discharge may occur to the charging member and the like.

Further, the single-layer sheets of comparative examples 1 to 5 were judged to induce electrostatic discharge because they exhibited surface resistance values of the conductive regions.

The surface resistance values of the multilayer sheets of comparative examples 2-1 and 2-2 showed the values of the electrostatic diffusion regions, but the humidity dependency was higher than those of examples 1-1 and 1-2 in which the contents of the polymer type antistatic agents in the surface layers were the same.

Further, it was confirmed that the surface layer of the multilayer sheet of comparative example 3 did not contain a polymer type antistatic agent and did not satisfy the antistatic condition.

From the above results, it was confirmed that the multilayer sheet and the plastic corrugated cardboard each having the polymer antistatic agent in the surface layer and the conductive carbon in the core layer exhibited a surface resistance value in the static electricity diffusing region, and the change in the surface resistance value was small with respect to humidity.

[ possibility of Industrial utilization ]

The present invention can be suitably used as a table board, a frame board, a partition board for partitioning a working area, and other articles in a clean room, a plastic corrugated cardboard, and the like.

Claims

1. A multilayer sheet made of a thermoplastic resin, characterized in that a first resin layer is formed from a thermoplastic resin composition containing conductive carbon at a concentration of 13 to 30 wt%, a second resin layer formed from a thermoplastic resin composition containing a polymer type antistatic agent is laminated on at least one of 2 plane parts of the first resin layer,

the first resin layer has a thickness of less than 1 × 10⁹Surface resistance value of Ω and the second resin layer has a value of 1 × 10⁵Omega is more than or equal to 1 multiplied by 10⁹Surface resistance value of Ω.

2. The thermoplastic-resin-made multilayer sheet according to claim 1, wherein said conductive carbon is carbon black.

3. The multilayer sheet according to claim 1, wherein the thermoplastic resin contained in at least one of the thermoplastic resin composition containing the conductive carbon and the thermoplastic resin composition containing the polymer-type antistatic agent is a polyolefin-based resin.

4. The thermoplastic-resin-made multilayered sheet according to claim 3, wherein the polyolefin-based resin is a polypropylene-based resin.

5. The multilayer sheet of claim 1, wherein the polymeric antistatic agent is at least 1 selected from the group consisting of a block copolymer of a polyether and a hydrophobic ester amide and a polyolefin-polyether block copolymer.

6. The multilayer sheet of claim 1, wherein the concentration of the polymeric antistatic agent in the second resin layer is in the range of 10 to 60 wt.%.

7. A corrugated cardboard structure made of a thermoplastic resin, comprising a thermoplastic resin composition for forming a first resin layer of a multilayer sheet made of a thermoplastic resin as described in any 1 of claims 1 to 5 and a second resin layer,

the thermoplastic resin composition forming the first resin layer forms a connecting part which is formed by 2 flat plate parts and a space part separating the 2 flat plate parts and bridges between 2 opposite surfaces of the 2 flat plate parts,

a second resin layer is laminated on at least one of 2 surfaces on the opposite side of the surfaces of the 2 flat plate parts facing each other.

8. A corrugated cardboard structure made of thermoplastic resin as claimed in claim 7, wherein the concentration of the polymer type antistatic agent in said second resin layer is in the range of 10 to 30% by weight.