WO2017060990A1 - Foam body and foam sheet - Google Patents

Abstract

Provided is a foam body having excellent resistance to corrosion by metals and excellent adhesiveness to an adherend even if an adhesive layer is not provided. This foam body is formed from a thermoplastic resin composition comprising a thermoplastic resin (a) and an azole ring-containing compound (b). The thermoplastic resin composition may further contain at least one type of surfactant. At least one type of polymer selected from the group consisting of acrylic polymer, rubber, urethane polymer, and ethylene-vinyl acetate copolymer is preferred as the thermoplastic resin (a).

Description

Foam and foam sheet

The present invention relates to a foam and a foam sheet excellent in adhesion to metal and corrosion resistance, and an electric / electronic device using the foam sheet.

Conventionally, an image display member fixed to an image display device such as a liquid crystal display, an electroluminescence display, a plasma display, a display member attached to a so-called “mobile phone”, “smart phone”, “portable information terminal”, camera, A foam material is used when an optical member such as a lens is fixed to a predetermined part (for example, a housing). Examples of such a foam material include a low-foam, fine-cell urethane-based foam having a closed cell structure and a product obtained by compression molding a highly foamed urethane, and a polyethylene-based foam having a closed cell and an expansion ratio of about 30 times. It was used. Specifically, for example, a gasket made of a polyurethane foam having a density of 0.3 to 0.5 g / cm ³ (see Patent Document 1) or an electric / electronic product made of a foamed structure having an average cell diameter of 1 to 500 μm. Equipment sealing materials (see Patent Document 2) and the like are used. Moreover, an adhesive-bonded foam sheet in which a pressure-sensitive adhesive is laminated or impregnated on a foam sheet is also known (see Patent Document 3).

In recent years, in addition to shock absorbing sheets used to prevent damage to display members, etc., as electronic devices such as PCs (personal computers), tablet PCs, PDAs (personal personal digital assistants), and mobile phones become more sophisticated. These members, for example, metal foils are laminated and incorporated. Thus, when laminating | stacking an impact-absorbing sheet and metal foil, the adhesiveness of an impact-absorbing sheet and metal foil and the corrosiveness of metal foil become a problem. In addition, due to the further thinning of electronic devices in recent years, it has become desirable to further reduce the thickness of members such as the impact absorbing sheet used therein, and the adhesiveness at the time of lamination of the impact absorbing sheet and the metal foil is desired. There is a need for no layering.

Also, as the products to which optical members (image display devices, cameras, lenses, etc.) are mounted are becoming thinner and thinner, the clearance of the part where the foam material is used tends to decrease remarkably. As the clearance decreases, it is necessary to reduce the thickness of the foamed member. However, when the thickness of the conventional foamed material is reduced, sufficient shock absorption is not exhibited. Therefore, for example, when an electric / electronic device with a display member such as “smartphone” is dropped on the ground or the like, there is a demand for a foam sheet that absorbs an impact at the time of collision and prevents the display member from being damaged.

Japanese Patent Laid-Open No. 2001-100216 JP 2002-309198 A Japanese Patent No. 2633714

An object of the present invention is to use a foam having excellent corrosion resistance to metals and excellent adhesion to an adherend without providing an adhesive layer, a foam sheet comprising the foam, and the foam sheet. It is to provide a laminated body and electrical / electronic equipment.
Another object of the present invention is to provide a foam exhibiting excellent impact absorbability even when the thickness is very small in addition to the above characteristics, a foam sheet comprising the foam, and a laminate using the foam sheet It is to provide body and electrical / electronic equipment.

As a result of intensive studies to achieve the above object, the present inventors have found that a foam formed from a thermoplastic resin composition containing an azole ring-containing compound is not only excellent in corrosion resistance to metals, but is also adhered. The present invention was completed by finding that the adhesion strength increases with time when it is attached to the body.

That is, the present invention provides a foam formed from a thermoplastic resin composition containing a thermoplastic resin (a) and an azole ring-containing compound (b).

The thermoplastic resin composition may further contain at least one surfactant.

The thermoplastic resin (a) is preferably at least one polymer selected from the group consisting of acrylic polymers, rubbers, urethane polymers, and ethylene-vinyl acetate copolymers.

The azole ring-containing compound is preferably at least one compound selected from benzotriazole compounds and benzothiazole compounds.

The content of the azole ring-containing compound (b) in the thermoplastic resin composition is, for example, 0.2 to 5 parts by weight with respect to 100 parts by weight of the thermoplastic resin (a).

It is preferable that the thermoplastic resin composition is a water-dispersed thermoplastic resin composition.

The foam has a density of 0.2 to 0.7 g / cm ³ , an average cell diameter of 10 to 150 μm, and a ratio of storage elastic modulus to loss elastic modulus at an angular frequency of 1 rad / s in dynamic viscoelasticity measurement. A certain loss tangent (tan δ) may have a peak top in the range of −30 ° C. to 30 ° C. In this case, the maximum value of the loss tangent (tan δ) in the range of −30 ° C. to 30 ° C. is preferably 0.2 or more.

The foam may have an initial elastic modulus of 5 N / mm ² or less in a tensile test at a tensile rate of 300 mm / min in a 23 ° C. environment.

The present invention also provides a foam sheet comprising the foam.

The thickness of the foam sheet is, for example, 30 to 500 μm.

The adhesive strength to the copper foil (peeling angle 180 °, tensile speed 300 m / min) after the foam sheet is bonded to the copper foil and left at 80 ° C. for 1 day is preferably 2 N / 20 mm or more.

The foamed sheet is formed by mechanically foaming a water-dispersed thermoplastic resin composition containing the thermoplastic resin (a) and the azole ring-containing compound (b), and a mechanically foamed water-dispersed type. It may be formed through a process B in which the resin composition is applied onto a substrate and dried.

The foamed sheet is used, for example, as an impact absorbing sheet for electric / electronic devices.

The present invention further provides a laminate of the foam sheet and the heat conductive layer.

The present invention further provides an electric / electronic device in which the foam sheet or the laminate is used. This electric / electronic device is an electric / electronic device provided with a display member, and has a structure in which the foam sheet or the laminate is sandwiched between a casing of the electric or electronic device and the display member. It may be a thing.

According to the present invention, since the foam is formed from the thermoplastic resin composition containing the azole ring-containing compound, not only is it excellent in corrosion resistance to metals, but even without providing an adhesive layer, When affixed to the adherend, the adhesion (adhesion) with the adherend increases with time. This is presumably because the azole ring-containing compound contained in the foam moves to the interface with the adherend and interacts with the adherend. Therefore, it is possible to prevent positional deviation and peeling from the adherend, and it is possible to reduce the thickness by eliminating the need for an adhesive layer, and the thickness of other functional members can be ensured accordingly.
In addition, when the foam has a specific density, a specific average cell diameter, and the loss tangent (tan δ) has a peak top in a specific temperature range, even if the thickness is small, the shock absorption is excellent. Even if an electric / electronic device using a foam sheet made of the foam of the present invention falls on the ground or the like, damage to the display or the like due to impact can be prevented.

It is a schematic explanatory drawing of a copper corrosion test.

[Foam]
The foam of the present invention is formed from a thermoplastic resin composition containing a thermoplastic resin (a) and an azole ring-containing compound (b).

[Thermoplastic resin (a)]
In the present invention, a thermoplastic resin is used as the resin material (polymer) constituting the foam. It does not specifically limit as a thermoplastic resin, The well-known thru | or well-known thermoplastic resin which can comprise a foam can be used. Examples of the thermoplastic resin include acrylic polymers, rubbers, urethane polymers, and ethylene-vinyl acetate copolymers. Among these, acrylic polymers, rubbers, and urethane polymers are preferable from the viewpoint of impact absorption. The thermoplastic resin constituting the foam may be one kind alone, or two or more kinds.

The acrylic polymer contains (meth) acrylic acid alkyl ester as a main component. Although it does not specifically limit as said (meth) acrylic-acid alkylester, For example, (meth) acrylic-acid methyl, (meth) acrylic-acid ethyl, (meth) acrylic-acid propyl, (meth) acrylic-acid isopropyl, (meth) acrylic Acid butyl, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, ( Heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, Isodecyl (meth) acrylate, undecyl (meth) acrylate, (meta Dodecyl acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, (meth) acrylic Examples thereof include (meth) acrylic acid alkyl esters having an alkyl group having 1 to 20 carbon atoms, such as isostearyl acid, nonadecyl (meth) acrylate, and eicosyl (meth) acrylate. The said (meth) acrylic-acid alkylester can be used individually or in combination of 2 or more types.

The ratio of (meth) acrylic acid alkyl ester (for example, (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms) to the total amount of monomer components (all monomer components) constituting the acrylic polymer is as follows: For example, it is 50% by weight or more, preferably 60% by weight or more, more preferably 80% by weight or more, and further preferably 85% by weight or more. The upper limit of the ratio of the (meth) acrylic acid alkyl ester to the total amount of monomer components constituting the acrylic polymer is, for example, 100% by weight, preferably 98% by weight, and more preferably 96% by weight.

The acrylic polymer may be a polymer containing only the (meth) acrylic acid alkyl ester as a constituent monomer component, but it is possible to impart functions according to necessity, more appropriately in adhesive properties. From the point of control, the monomer component may be a polymer containing a copolymerizable monomer copolymerizable therewith with the above (meth) acrylic acid alkyl ester. A copolymerizable monomer can be used individually by 1 type or in combination of 2 or more types.

Examples of the copolymerizable monomer include polar group-containing monomers. Although it does not specifically limit as said polar group containing monomer, For example, a nitrogen atom containing monomer, a carboxyl group containing monomer, a hydroxyl group containing monomer, a sulfonic acid group containing monomer, a phosphoric acid group containing monomer etc. are mentioned. A polar group containing monomer can be used individually by 1 type or in combination of 2 or more types.

The nitrogen atom-containing monomer is not particularly limited as long as it is a monomer (polymerizable compound) having a nitrogen atom and an ethylenically unsaturated bond in the molecule. For example, a cyano group-containing monomer such as (meth) acrylonitrile; (2-hydroxyethyl) (meth) acrylamide, N- (2-hydroxypropyl) (meth) acrylamide, N- (1-hydroxypropyl) (meth) acrylamide, N- (3-hydroxypropyl) (meth) acrylamide, N-hydroxyalkyl (meth) acrylamides such as N- (2-hydroxybutyl) (meth) acrylamide, N- (3-hydroxybutyl) (meth) acrylamide, N- (4-hydroxybutyl) (meth) acrylamide; N -(Meth) acryloylmorpholine, N- (meth) acrylo Cyclic (meth) acrylamides such as Rupirorijin; (meth) acrylamide, N- substituted (meth) include acyclic (meth) acrylamide such as acrylamide. Examples of the N-substituted (meth) acrylamide include N-alkyl (meth) acrylamides such as N-ethyl (meth) acrylamide and Nn-butyl (meth) acrylamide; N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) acrylamide, N, N-diisopropyl (meth) acrylamide, N, N-di (n-butyl) (meth) acrylamide, N, N-di (t And N, N-dialkyl (meth) acrylamide such as (butyl) (meth) acrylamide.

Further, examples of the nitrogen atom-containing monomer include N-vinyl-2-pyrrolidone (NVP), N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, and N-vinyl. N-vinyl cyclic amides such as 1,3-oxazin-2-one and N-vinyl-3,5-morpholinedione; aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, Monomers having amino groups such as N-dimethylaminopropyl (meth) acrylate; monomers having a maleimide skeleton such as N-cyclohexylmaleimide and N-phenylmaleimide; N-methylitaconimide, N-ethylitaconimide, N-butylitacon Imido, N-2-ethylhexylitaconimide, N-laur Ruitakon'imido and itaconimide monomers such as N- cyclohexyl itaconic imide. A nitrogen atom containing monomer can be used individually by 1 type or in combination of 2 or more types.

The carboxyl group-containing monomer is a monomer having one or more carboxyl groups in one molecule, but may be in the form of an anhydride. Although it does not specifically limit as said carboxyl group containing monomer, For example, (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, maleic anhydride, itaconic anhydride etc. are mentioned. A carboxyl group-containing monomer can be used individually by 1 type or in combination of 2 or more types.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, ( 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl methacrylate Etc. Of these, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate are preferable. A hydroxyl-containing monomer can be used individually by 1 type or in combination of 2 or more types.

Examples of the sulfonic acid group-containing monomer include styrene sulfonic acid, allyl sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalene sulfonic acid, and the like. A sulfonic acid group containing monomer can be used individually by 1 type or in combination of 2 or more types.

Examples of the phosphate group-containing monomer include 2-hydroxyethyl acryloyl phosphate. In addition, a phosphate group containing monomer can be used individually by 1 type or in combination of 2 or more types.

The blending proportion of the polar group-containing monomer in the monomer component constituting the acrylic polymer (total proportion in the case of two or more types) is not particularly limited, but with respect to the total amount of monomer components constituting the acrylic polymer, The lower limit is more preferably 3% by weight, and the upper limit is more preferably 20% by weight. Further, as the polar group-containing monomer, it is preferable to use at least a nitrogen atom-containing monomer. The blending ratio of the nitrogen atom-containing monomer is preferably 1 to 30% by weight with respect to the total amount of monomer components constituting the acrylic polymer, the lower limit is more preferably 3% by weight, and the upper limit is more preferably 20% by weight. When the blending ratio of the polar group-containing monomer is within the above range, the cohesive force of the pressure-sensitive adhesive layer becomes appropriate, and high holding force and adhesive force can be obtained.

In addition to the above, the copolymerizable monomer has an alicyclic hydrocarbon group such as cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, bornyl (meth) acrylate, isobornyl (meth) acrylate, etc. ) Acrylate; phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, (meth) acrylate (meth) acrylate having an aromatic hydrocarbon group such as phenoxydiethylene glycol; (meth) acrylic acid 2- Monomers having an alkoxyalkyl group such as methoxyethyl, 3-methoxypropyl (meth) acrylate, methoxyethylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate; Monomers having an epoxy group such as (meth) acrylate and allyl glycidyl ether; styrene monomers such as styrene and α-methylstyrene; α-olefins such as ethylene, propylene, isoprene, butadiene and isobutylene; 2-isocyanatoethyl acrylate, Monomers having an isocyanate group such as 2-isocyanatoethyl methacrylate; Vinyl ester monomers such as vinyl acetate and vinyl propionate; Vinyl ether monomers such as vinyl ether; Heterocycles such as tetrahydrofurfuryl (meth) acrylate (meth) Acrylic acid ester; Monomer having halogen atom such as (meth) acrylate having fluorine atom; 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxy Monomers having an alkoxysilyl group such as orchids; and a monomer having a siloxane bond such as silicone (meth) acrylate.

Moreover, a polyfunctional monomer can be used as the copolymerizable monomer. According to such a polyfunctional monomer, a crosslinked structure can be introduced into the acrylic polymer, and the cohesive force of the pressure-sensitive adhesive layer can be adjusted. Examples of the polyfunctional monomer include hexanediol di (meth) acrylate, butanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, and neopentyl glycol. Di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, allyl Examples include (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, and urethane acrylate. The polyfunctional monomer is preferably a polyfunctional acrylic monomer. In addition, the said polyfunctional monomer can be used individually or in combination of 2 or more types.

The rubber may be natural rubber or synthetic rubber. Examples of the rubber include nitrile rubber (NBR), methyl methacrylate-butadiene rubber (MBR), styrene-butadiene rubber (SBR), acrylic rubber (ACM, ANM), urethane rubber (AU), and silicone rubber. Among these, nitrile rubber (NBR), methyl methacrylate-butadiene rubber (MBR), and silicone rubber are preferable.

Examples of the urethane polymer include polycarbonate polyurethane, polyester polyurethane, and polyether polyurethane.

As the ethylene-vinyl acetate copolymer, a known or well-known ethylene-vinyl acetate copolymer can be used.

In the present invention, it is preferable that the surface has tackiness when a foam (foamed sheet) is formed. When the surface of the foam (foamed sheet) has tackiness, it can be laminated with good adhesion to the adherend without providing an adhesive layer. As a method for imparting tackiness to the surface of a foam (foamed sheet), for example, as a monomer constituting the thermoplastic resin (a) (for example, acrylic polymer) constituting the foam, the Tg of the homopolymer is − A monomer having a temperature of less than 10 ° C. (for example, −70 ° C. or more and less than −10 ° C., preferably −70 ° C. to −12 ° C., more preferably −65 ° C. to −15 ° C.) is added to the thermoplastic resin (a) (eg, acrylic For example, 70 to 98% by weight (the lower limit is preferably 75% by weight and the upper limit is preferably 97% by weight) is used with respect to all monomer components (total amount of monomer components) constituting the polymer), and other monomers are appropriately used. The method of selecting and using is mentioned.

In the present invention, as will be described later, as the thermoplastic resin, a loss tangent (tan δ) which is a ratio of a storage elastic modulus and a loss elastic modulus at an angular frequency of 1 rad / s in the dynamic viscoelasticity measurement of the foam. A thermoplastic resin having a peak top in the range of −30 ° C. to 30 ° C. is preferable. By using such a thermoplastic resin, the impact absorbability of the foam can be improved. In order to set the peak top of the loss tangent (tan δ) in the range of −30 ° C. or higher and 30 ° C. or lower, the Tg of the thermoplastic resin can be used as an index or a standard. For example, the thermoplastic resin has a Tg of −50 ° C. or more and less than 50 ° C. (the lower limit is preferably −40 ° C., more preferably −30 ° C., and the upper limit is preferably 40 ° C., more preferably 30 ° C.). It is preferred to select from a range of polymers.

From such a viewpoint, for example, when the thermoplastic resin is an acrylic polymer, the acrylic polymer includes a monomer having a homopolymer Tg of −10 ° C. or more and a monomer having a homopolymer Tg of less than −10 ° C. An acrylic polymer formed as an essential monomer component is preferred. Using such an acrylic polymer, the ratio of the storage elastic modulus and loss elastic modulus at an angular frequency of 1 rad / s in dynamic viscoelasticity measurement is obtained by adjusting the amount ratio of the former monomer and the latter monomer. A foam having a loss tangent (tan δ) peak top in the range of −30 ° C. to 30 ° C. can be obtained relatively easily.

In the present invention, “Tg of homopolymer” means “glass transition temperature (Tg) of homopolymer of the monomer”, specifically, “Polymer Handbook” (3rd edition, John Wiley & Sons). , Inc, 1987). The Tg of a homopolymer of a monomer not described in the above document refers to, for example, a value obtained by the following measurement method (see JP 2007-51271 A). That is, in a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux condenser, 100 parts by weight of monomer, 0.2 part by weight of 2,2′-azobisisobutyronitrile, and ethyl acetate 200 as a polymerization solvent. A part by weight is charged and stirred for 1 hour while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, the temperature is raised to 63 ° C. and the reaction is carried out for 10 hours. Next, the mixture is cooled to room temperature to obtain a homopolymer solution having a solid concentration of 33% by weight. Next, this homopolymer solution is cast-coated on a separator and dried to prepare a test sample (sheet-like homopolymer) having a thickness of about 2 mm. This test sample was punched into a disk shape having a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to a shear strain at a frequency of 1 Hz using a viscoelasticity tester (ARES, manufactured by Rheometrics). Viscoelasticity is measured in a shear mode at a heating rate of 150 ° C. and 5 ° C./min, and the peak top temperature of tan δ is defined as Tg of the homopolymer. The Tg of the thermoplastic resin can also be measured by this method.

In a monomer having a homopolymer Tg of −10 ° C. or higher, the Tg is, for example, −10 ° C. to 250 ° C., preferably 10 to 230 ° C., more preferably 50 to 200 ° C.

Examples of the homopolymer having a Tg of −10 ° C. or more include, for example, (meth) acrylonitrile; amide group-containing monomers such as (meth) acrylamide and N-hydroxyethyl (meth) acrylamide; (meth) acrylic acid; methacrylic acid (Meth) acrylic acid alkyl ester having a Tg of −10 ° C. or more of homopolymer such as methyl and ethyl methacrylate; (meth) acrylate having an alicyclic hydrocarbon group such as isobornyl (meth) acrylate; N-vinyl— Examples thereof include heterocyclic ring-containing vinyl monomers such as 2-pyrrolidone (N-vinyl cyclic amide and the like); hydroxyl group-containing monomers such as 2-hydroxyethyl methacrylate and the like. These can be used individually by 1 type or in combination of 2 or more types. Among these, (meth) acrylonitrile (especially acrylonitrile) is particularly preferable. When (meth) acrylonitrile (especially acrylonitrile) is used as a monomer having a homopolymer Tg of −10 ° C. or higher, the peak top strength of the loss tangent (tan δ) of the foam is increased because of the strong intermolecular interaction. be able to.

In a monomer having a Tg of less than −10 ° C., the Tg is, for example, −70 ° C. or more and less than −10 ° C., preferably −70 ° C. to −12 ° C., more preferably −65 ° C. to −15 ° C. .

Examples of the homopolymer having a Tg of less than −10 ° C. include, for example, (meth) acrylic acid alkyl esters having a homopolymer Tg of less than −10 ° C., such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc. Is mentioned. These can be used individually by 1 type or in combination of 2 or more types. Among these, an acrylic acid alkyl ester having an alkyl group having 2 to 8 carbon atoms is particularly preferable.

The content of the monomer having a Tg of the homopolymer of −10 ° C. or more with respect to the total amount of the monomer components constituting the acrylic polymer is preferably 2 to 30% by weight. The lower limit is more preferably 3% by weight, still more preferably 4% by weight, and the upper limit is more preferably 25% by weight, still more preferably 20% by weight. Further, the content of the monomer having a Tg of the homopolymer of less than −10 ° C. with respect to the total amount of the monomer components constituting the acrylic polymer is preferably 70 to 98% by weight. The lower limit is more preferably 75% by weight, still more preferably 80% by weight, and the upper limit is more preferably 97% by weight, still more preferably 96% by weight.

[Azolic ring-containing compound (b)]
The azole ring-containing compound (b) may be a compound having a 5-membered ring containing one or more nitrogen atoms in the ring, for example, a diazole (imidazole, pyrazole) ring, triazole ring, tetrazole ring, oxazole ring. , A compound having an isoxazole ring, a thiazole ring, or an isothiazole ring. These rings may be condensed with an aromatic ring such as a benzene ring to form a condensed ring. Examples of the compound having such a condensed ring include a compound having a benzimidazole ring, a benzopyrazole ring, a benzotriazole ring, a benzoxazole ring, a benzoisoxazole ring, a benzothiazole ring, or a benzoisothiazole ring.

The azole ring and the condensed ring (benzotriazole ring, benzothiazole ring, etc.) each may have a substituent. Examples of the substituent include alkyl groups having 1 to 6 carbon atoms (preferably 1 to 3 carbon atoms) such as methyl group, ethyl group, propyl group, isopropyl group and butyl group; methoxy group, ethoxy group, isopropyloxy An alkoxy group having 1 to 12 carbon atoms (preferably 1 to 3 carbon atoms) such as a butoxy group; an aryl group having 6 to 10 carbon atoms such as a phenyl group, a tolyl group or a naphthyl group; an amino group; a methylamino group; (Mono or di) C _1-10 alkylamino group such as dimethylamino group; amino-C _1-6 alkyl group such as aminomethyl group, 2-aminoethyl group; N, N-diethylaminomethyl group, N, N— Mono or di (C _1-10 alkyl) amino-C _1-6 alkyl group such as bis (2-ethylhexyl) aminomethyl group; mercapto group; carbon number of 1 such as methoxycarbonyl group and ethoxycarbonyl group A carboxy-C _1-6 alkyl group such as a carboxymethyl group; a carboxy-C _1-6 alkylthio group such as a 2-carboxyethylthio group; N, N-bis (hydroxymethyl) N, N-bis (hydroxy-C _1-4 alkyl) amino-C _1-4 alkyl group such as aminomethyl group; sulfo group and the like. The azole ring-containing compound (b) may form a salt such as a sodium salt or a potassium salt.

In the present invention, a compound in which an azole ring forms a condensed ring with an aromatic ring such as a benzene ring from the point of rust prevention action on a metal is preferable. Among them, a benzotriazole-based compound (a compound having a benzotriazole ring), A benzothiazole compound (a compound having a benzothiazole ring) is particularly preferable.

Examples of the benzotriazole compounds include 1,2,3-benzotriazole, methylbenzotriazole, carboxybenzotriazole, carboxymethylbenzotriazole, and 1- [N, N-bis (2-ethylhexyl) aminomethyl] benzotriazole. 1- [N, N-bis (2-ethylhexyl) aminomethyl] methylbenzotriazole, 2,2 ′-[[(methyl-1H-benzotriazol-1-yl) methyl] imino] bisethanol, or these A sodium salt etc. are mentioned.

Examples of the benzothiazole compound include 2-mercaptobenzothiazole, 3- (2- (benzothiazolyl) thio) propionic acid, or a sodium salt thereof.

The azole ring-containing compound (b) may be used alone or in combination of two or more.

The content [solid content (nonvolatile content)] of the azole ring-containing compound (b) in the thermoplastic resin composition for forming the foam of the present invention impairs the adhesion to the adherend and the original properties of the foam. For example, 0.2 to 5 parts by weight is preferable with respect to 100 parts by weight of the thermoplastic resin (a) [solid content (nonvolatile content)]. The lower limit is more preferably 0.3 parts by weight, still more preferably 0.4 parts by weight, and the upper limit is more preferably 3 parts by weight, still more preferably 2 parts by weight. When the content of the azole ring-containing compound (b) is in the above range, it is possible to achieve both high levels of corrosion resistance to metal and adhesion to an adherend.

[Additive]
In the thermoplastic resin composition for forming the foam of the present invention, in addition to the thermoplastic resin (a) and the azole ring-containing compound (b), a surfactant, a crosslinking agent, and a thickening agent are added as necessary. Agents and other additives may be included.

For example, the thermoplastic resin composition may contain an optional surfactant for reducing the bubble diameter and stabilizing the foamed foam. The surfactant is not particularly limited, and any of an anionic surfactant, a cationic surfactant, a nonionic surfactant, an amphoteric surfactant, and the like may be used. From the viewpoint of the stability of the foam, an anionic surfactant is preferable, and a fatty acid ammonium surfactant such as ammonium stearate is more preferable. Surfactant may be used individually by 1 type and may be used in combination of 2 or more type. Different surfactants may be used in combination, for example, an anionic surfactant and a nonionic surfactant, or an anionic surfactant and an amphoteric surfactant may be used in combination.

The addition amount [solid content (nonvolatile content)] of the surfactant is, for example, 0 to 10 parts by weight with respect to 100 parts by weight of the thermoplastic resin (a) [solid content (nonvolatile content)]. Preferably it is 0.5 part by weight, more preferably 1 part by weight, and the upper limit is preferably 8 parts by weight, more preferably 6 parts by weight.

In addition, the thermoplastic resin composition may contain an arbitrary cross-linking agent in order to improve the strength, heat resistance and moisture resistance of the foam. The crosslinking agent is not particularly limited, and any of oil-soluble and water-soluble may be used. Examples of the crosslinking agent include epoxy, oxazoline, isocyanate, carbodiimide, melamine, and metal oxide. Among these, an oxazoline-based crosslinking agent is preferable.

The addition amount [solid content (nonvolatile content)] of the crosslinking agent is, for example, 0 to 10 parts by weight with respect to 100 parts by weight of the thermoplastic resin (a) [solid content (nonvolatile content)], and the lower limit is preferably Is 0.01 part by weight, more preferably 0.1 part by weight, and the upper limit is preferably 9 parts by weight, more preferably 8 parts by weight.

Furthermore, the thermoplastic resin composition may contain an arbitrary thickener for improving the stability of the foamed foam and the film-forming property. The thickener is not particularly limited, and examples thereof include acrylic acid type, urethane type, and polyvinyl alcohol type. Of these, polyacrylic acid thickeners are preferred.

The addition amount of the thickener [solid content (nonvolatile content)] is, for example, 0 to 10 parts by weight with respect to 100 parts by weight of the thermoplastic resin (a) [solid content (nonvolatile content)]. Preferably it is 0.1 weight part, More preferably, it is 0.3 weight part, An upper limit becomes like this. Preferably it is 6 weight part, More preferably, it is 3 weight part.

Further, the thermoplastic resin composition may contain any appropriate other component as long as it does not impair the corrosion resistance to metal, adhesion to the adherend, and the original properties of the foam. . Such other components may contain only 1 type and may contain 2 or more types. Examples of the other components include polymer components other than the thermoplastic resin (a), softeners, antioxidants, anti-aging agents, rust inhibitors, gelling agents, curing agents, plasticizers, fillers, and reinforcing agents. , Foaming agents, flame retardants, light stabilizers, ultraviolet absorbers, colorants (such as pigments and dyes), pH adjusters, thermal polymerization initiators, photopolymerization initiators, and the like.

Examples of the filler include silica, clay (mica, talc, smectite, etc.), alumina, titania, zinc oxide, tin oxide, zeolite, graphite, carbon nanotube, inorganic fiber (carbon fiber, glass fiber, etc.), and organic fiber. And metal powder (silver, copper, etc.). In addition, piezoelectric particles (such as titanium oxide), conductive particles, thermally conductive particles (such as boron nitride), and organic fillers (such as silicone powder) can be added as fillers.

The thermoplastic resin composition may be any of a water-dispersed thermoplastic resin composition, a solvent-type thermoplastic resin composition, and a thermoplastic resin composition that does not contain water and a solvent.

The foam of the present invention can be produced by subjecting the thermoplastic resin composition to foaming. The foam sheet of the present invention can be produced by subjecting the thermoplastic resin composition to foam molding and forming a sheet. As the foaming method (bubble forming method), methods usually used for foam molding, such as physical methods and chemical methods, can be employed. In general, the physical method is to disperse a gas component such as air or nitrogen in a polymer solution and form bubbles by mechanical mixing. The chemical method is a method of obtaining a foam by forming cells with a gas generated by thermal decomposition of a foaming agent added to a polymer base. From the viewpoint of environmental problems, a physical method is preferable. Bubbles formed by physical methods are often open cells.

As a thermoplastic resin composition to be subjected to foaming (foam molding), a thermoplastic resin composition not containing water and a solvent, or a resin solution (solvent type thermoplastic resin composition) in which a thermoplastic resin is dissolved in a solvent is used. However, from the viewpoint of cellularity, it is preferable to use an emulsion (water-dispersed thermoplastic resin composition) containing a thermoplastic resin. As an emulsion, you may blend and use 2 or more types of emulsion.

The solid content concentration of the emulsion is preferably higher from the viewpoint of film formability. The solid content concentration of the emulsion is preferably 30% by weight or more, more preferably 40% by weight or more, and further preferably 50% by weight or more.

In the present invention, a method of producing a foam through a step of foaming mechanically foaming a water-dispersed thermoplastic resin composition (emulsion resin composition) (step A) is preferable. The foaming device is not particularly limited, and examples thereof include a high-speed shearing method, a vibration method, and a pressurized gas discharge method. Among these, the high-speed shearing method is preferable from the viewpoint of finer bubble diameter and production of a large capacity.

Bubbles when foamed by mechanical stirring are gas (gas) taken into the emulsion. The gas is not particularly limited as long as it is inert to the emulsion, and examples thereof include air, nitrogen, carbon dioxide and the like. Among these, air is preferable from the viewpoint of economy.

The foamed sheet of the present invention can be obtained through a step (Step B) in which the emulsion resin composition foamed by the above method is applied onto a substrate and dried. The substrate is not particularly limited, and examples thereof include a peeled plastic film (such as a peeled polyethylene terephthalate film), a plastic film (such as a polyethylene terephthalate film), and a heat conductive layer (such as a heat conductive layer described below). Can be mentioned.

In the step B, a general method can be adopted as a coating method and a drying method. Step B includes a preliminary drying step B1 for drying the bubble-containing emulsion resin composition applied on the substrate at 50 ° C. or higher and lower than 125 ° C., and then a main drying step B2 for further drying at 125 ° C. or higher and 200 ° C. or lower. Preferably it is.

By providing the preliminary drying step B1 and the main drying step B2, it is possible to prevent the bubbles from being coalesced and the bubbles to burst due to a rapid temperature rise. In particular, in the foam sheet having a small thickness, bubbles are united or ruptured due to a rapid rise in temperature, and therefore, the provision of the preliminary drying step B1 is significant. The temperature in the preliminary drying step B1 is preferably 50 ° C. or higher and 100 ° C. or lower. The time of the preliminary drying step B1 is, for example, 0.5 minutes to 30 minutes, preferably 1 minute to 15 minutes. Moreover, the temperature in this drying process B2 becomes like this. Preferably they are 130 degreeC or more and 180 degrees C or less. The time of the main drying step B2 is, for example, 0.5 minutes to 30 minutes, preferably 1 minute to 15 minutes.

The foam of the present invention has a density of 0.2 to 0.7 g / cm ³ , an average cell diameter of 10 to 150 μm, and a storage elastic modulus and a loss elastic modulus at an angular frequency of 1 rad / s in dynamic viscoelasticity measurement. It is preferable that the loss tangent (tan δ) as a ratio has a peak top in the range of −30 ° C. to 30 ° C. Such a foam has high shock absorption. In the present specification, the density of the foam means “apparent density”.

The lower limit of the density of the foam is more preferably 0.21 g / cm ³ , still more preferably 0.22 g / cm ³ , and the upper limit is more preferably 0.6 g / cm ³ , still more preferably 0.5 g. / Cm ³ , particularly preferably 0.4 g / cm ³ . When the density of the foam is 0.2 g / cm ³ or more, high strength can be maintained, and when it is 0.7 g / cm ³ or less, high impact absorbability is exhibited. Further, when the density of the foam is in the range of 0.2 to 0.4 g / cm ³ , an even higher impact absorbability is exhibited. The density of the foam can be adjusted to a density of 0.2 to 0.7 g / cm ³ by adjusting the amount of gas (gas) component taken into the emulsion resin composition during mechanical stirring.

The lower limit of the average cell diameter of the foam is more preferably 15 μm, still more preferably 20 μm, and the upper limit is more preferably 140 μm, still more preferably 130 μm. When the average cell diameter is 10 μm or more, excellent impact absorbability is exhibited. Moreover, when the average cell diameter is 150 μm or less, excellent compression recovery is obtained. The average cell diameter of the foam can be set in the range of 10 to 150 μm by adjusting the type and amount of the surfactant and by adjusting the stirring speed and stirring time during mechanical stirring.

As described above, the peak top of the loss tangent (tan δ), which is the ratio of the storage elastic modulus and the loss elastic modulus at an angular frequency of 1 rad / s in the dynamic viscoelasticity measurement of the foam, is −30 ° C. or higher and 30 ° C. or higher. It is preferable to be in the following range. The lower limit of the temperature range where the loss tangent peak top exists is more preferably −25 ° C., further preferably −20 ° C., and the upper limit is more preferably 20 ° C., and further preferably 10 ° C. In the case of a material having two or more peak tops of loss tangents, it is desirable that at least one of them falls within the above range. When the peak temperature is −30 ° C. or higher, excellent compression recovery is exhibited. Moreover, when the peak temperature is 30 ° C. or lower, high flexibility is exhibited and excellent shock absorption is exhibited.

The peak top strength (maximum value) of loss tangent (tan δ) in the range of −30 ° C. or higher and 30 ° C. or lower is preferably higher from the viewpoint of shock absorption, for example, 0.2 or higher, preferably 0.3 or higher. The upper limit value of the peak top intensity (maximum value) is, for example, 2.0.

Thus, the peak temperature and peak top strength of the loss tangent (tan δ) greatly contribute to the shock absorption of the foam. When the peak top of the loss tangent (tan δ), which is the ratio of the storage elastic modulus and loss elastic modulus at the angular frequency of 1 rad / s in the dynamic viscoelasticity measurement of the foam, is in the range of −30 ° C. or higher and 30 ° C. or lower, The reason why the foam sheet has high impact absorbability is not necessarily clear, but it is presumed that the loss tangent (tan δ) peak exists at a location that matches the frequency of impact. That is, the range where the loss tangent (tan δ) is −30 ° C. or higher and 30 ° C. or lower is converted to the frequency range corresponding to the drop impact of the structure by the temperature-time conversion rule in the viscoelasticity measurement. It is presumed that the shock absorption becomes higher as the foamed sheet has a peak temperature of the loss tangent (tan δ) in the range of 30 ° C. or lower. The storage elastic modulus is a repulsive force with respect to the impact energy applied to the foam sheet. If the storage elastic modulus is high, the impact is repelled as it is. On the other hand, the loss elastic modulus is a physical property that changes impact energy applied to the foam sheet to heat, and the higher the loss elastic modulus is, the more the impact energy is changed to heat, so the impact is absorbed and the strain is reduced. From this, it is surmised that a foam sheet having a larger loss tangent (tan δ), which is a ratio of the storage elastic modulus and the loss elastic modulus, has a higher impact absorption rate by changing the impact to heat and reducing the repulsive force. .

The initial elastic modulus of the foam is preferably low from the viewpoint of impact absorption. The initial elastic modulus (a value calculated from a slope at the time of 10% strain in a tensile test under a 23 ° C. environment and a tensile speed of 300 mm / min) is preferably 5 N / mm ² or less, more preferably 3 N / mm ^2. It is as follows. The lower limit value of the initial elastic modulus is, for example, 0.1 N / mm ² .

The foam can be formed by subjecting the thermoplastic resin composition to foaming, but the foamed resin composition (solid matter) [molded without foaming the thermoplastic resin composition] The peak top of the loss tangent (tan δ), which is the ratio of the storage elastic modulus to the loss elastic modulus at an angular frequency of 1 rad / s in the dynamic viscoelasticity measurement, is preferably in the range of −30 ° C. to 30 ° C. The lower limit of the temperature range where the peak tangent of the loss tangent exists is more preferably −20 ° C., further preferably −10 ° C., and the upper limit is more preferably 20 ° C., further preferably 10 ° C. In the case of a material having two or more peak tops of loss tangents, it is desirable that at least one of them falls within the above range. Loss tangent (tan δ) peak top strength of the resin composition (solid material) in the range of −30 ° C. to 30 ° C. (this value is the loss tangent of the foam in the range of −30 ° C. to less than 30 ° C. The peak top strength of (tan δ) is equivalent to a value obtained by dividing the peak top strength by the foam density (g / cm ³ ). Further, the initial elastic modulus (23 ° C., tensile speed 300 mm / min) of the unfoamed resin composition (solid material) is desirably lower, preferably 50 N / mm ² or less, more preferably 30 N / mm ^2. It is as follows. The lower limit value of the initial elastic modulus is, for example, 0.3 N / mm ² .

The cell structure of the foam may be any of an open cell structure, a closed cell structure, or a semi-continuous semi-closed cell structure. From the viewpoint of impact absorption, an open cell structure and a semi-open semi-closed cell structure are preferable.

[Foamed sheet]
The thickness of the foam sheet of the present invention is not particularly limited, and can be selected according to the application. For example, the thickness of the foam sheet is about 30 to 2000 μm. From the viewpoint of adapting to the minute clearance, the thickness of the foamed sheet is preferably in the range of 30 to 500 μm. The lower limit is more preferably 40 μm, still more preferably 50 μm, and the upper limit is more preferably 400 μm, still more preferably 300 μm. When the thickness of the foamed sheet is 30 μm or more, bubbles can be contained uniformly, and excellent shock absorption can be exhibited. Moreover, when the thickness of the foamed sheet is 500 μm or less, it is possible to easily follow a minute clearance.

The peak top of the loss tangent (tan δ), which is the ratio between the storage elastic modulus and the loss elastic modulus at an angular frequency of 1 rad / s in the dynamic viscoelasticity measurement of the foam as described above, is −30 ° C. or higher and 30 ° C. or lower. The foam sheet in the range has high shock absorption even if the thickness is as thin as 30 to 500 μm.

When the thickness of the foamed sheet is large to some extent, the impact absorption can be adjusted by selecting the average cell diameter, density, etc., but when the thickness of the foamed sheet is very small (for example, a thickness of 30 to 200 μm). ), It is not possible to absorb the shock sufficiently by adjusting these characteristics. This is because when the thickness of the foam sheet is very thin, the bubbles in the foam are immediately crushed by the impact and the shock buffering function by the bubbles is lost. When the peak top of the loss tangent (tan δ), which is the ratio of the storage elastic modulus and loss elastic modulus at an angular frequency of 1 rad / s in the dynamic viscoelasticity measurement of the foam, is in the range of −30 ° C. to 30 ° C. Even after the bubbles are crushed, the constituent material of the foam exerts the function of buffering the impact.

In the present invention, the ratio of the average cell diameter (μm) to the thickness of the foamed sheet (μm) (the former / the latter) is preferably in the range of 0.2 to 0.9 from the viewpoint of shock absorption. The lower limit of the ratio of the average cell diameter (μm) to the thickness of the foamed sheet (μm) is preferably 0.25, more preferably 0.3, and the upper limit is preferably 0.85, more preferably 0. .8.

When the foam sheet of the present invention is attached to an adherend such as a metal foil, the adhesive force to the adherend gradually increases with time. Therefore, high adhesion reliability can be obtained. For example, the adhesive strength to copper foil (peeling angle 180 °, tensile speed 300 m / min) after bonding the foam sheet of the present invention to copper foil and leaving it at 80 ° C. for 1 day is 2.0 N / 20 mm or more. Preferably, it is 2.5 N / 20 mm or more, more preferably 3.0 N / 20 mm or more, and still more preferably 3.5 N / 20 mm or more. In addition, the foam sheet of this invention can be adhere | attached on a plastic film, paper, a nonwoven fabric, etc. besides copper foil (metal foil).

In addition, the adhesive force to copper foil (initial adhesive force) (peeling angle 180 °, tensile speed 300 m / min) immediately after the foam sheet of the present invention is bonded to the copper foil is, for example, 0.03 N / 20 mm or more. Preferably, it may be about 0.03 to 1 N / 20 mm (or about 0.05 to 0.5 N / 20 mm).

The foamed sheet of the present invention may be provided with an adhesive layer (adhesive layer) on one or both sides of the foamed sheet, if necessary. It does not specifically limit as an adhesive which comprises an adhesive layer, For example, any of an acrylic adhesive, a rubber adhesive, a silicone adhesive, etc. may be sufficient. Moreover, when providing an adhesive layer, you may laminate | stack the release liner which protects an adhesive layer until the time of use on the surface. Since the foamed sheet of the present invention is excellent in adhesion to an adherend (metal member or the like), the member or the like can be fixed without providing an adhesive layer.

The foamed sheet of the present invention may be distributed on the market as a wound body (rolled material) wound in a roll shape.

Since the foamed sheet of the present invention contains an azole ring-containing compound as described above, corrosion of the metal can be prevented for a long time when it is placed in contact with a metal member such as a metal foil. Also, the azole ring-containing compound contained in the foamed sheet moves to the interface with the adjacent member (adhered body) and interacts with the adjacent member, or the adhesive force increases with time. Therefore, the adhesive layer is unnecessary and thinning is possible, and the thickness of the other material can be secured by the thickness of the adhesive layer. For this reason, for example, in electrical / electronic equipment, members for electrical / electronic equipment used when attaching (attaching) various members or components (eg, optical members) to a predetermined part (eg, housing) In particular, it is useful as a shock absorbing sheet. In particular, it is useful when the member (adhered body) on at least one surface side of the foam sheet is a metal member (for example, a metal foil such as a copper foil, an aluminum foil, a gold foil, or a silver foil).

As an optical member that can be attached (attached) using the foam sheet of the present invention, for example, an image display member attached to an image display device such as a liquid crystal display, an electroluminescence display, a plasma display (particularly, a small image display). Members), display members such as touch panels attached to mobile communication devices such as so-called “mobile phones”, “smartphones” and “portable information terminals”, cameras and lenses (particularly small cameras and lenses), etc. Can be mentioned.

[Laminate]
The laminate of the present invention is a laminate (sheet-like laminate) of a foam sheet (foam sheet layer) and a heat conductive layer. The thermal conductivity of the thermal conductive layer is preferably 200 W / m · K or more. The thermal conductivity is a value measured from a steady method. The thermal conductivity of the heat conductive layer is preferably 300 W / m · K or more, more preferably 400 W / m · K or more. When the thermal conductivity of the thermal conductive layer is 200 W / m · K or more, excellent thermal diffusibility (heat dissipation) is exhibited. A practical upper limit of the thermal conductivity is, for example, 1500 W / m · K.

The thickness of the heat conductive layer can be adjusted to any appropriate thickness depending on the purpose. The thickness of the heat conductive layer is preferably 5 μm or more, more preferably 7 μm or more. The upper limit of the thickness of the heat conductive layer is, for example, 130 μm, preferably 120 μm, and more preferably 110 μm.

Examples of the heat conductive layer include a graphite sheet and a metal foil. Examples of the metal foil material include aluminum, gold, silver, and copper. As the metal foil, an aluminum foil, a copper foil or the like having a high far-infrared reflectance and a low process cost is preferable.

As a method for producing the laminated body, a method of transferring (attaching) a foam sheet to a heat conductive layer, applying the foamed emulsion resin composition to a heat conductive layer, and drying to form a foam sheet layer The method of doing is mentioned. The latter method produces higher adhesive strength than the former method.

According to the laminate of the present invention, since it has a foam sheet and a heat conductive layer, it is excellent in impact absorption and thermal diffusibility (heat dissipation). Moreover, since the adhesive force between the foam sheet and the heat conductive layer and the adhesive force between the adjacent member and the foam sheet when using the laminate of the present invention increase with time, the adhesive reliability is excellent. Further, when the heat conductive layer is a metal, corrosion of the metal can be prevented for a long time when the metal and the adjacent member when using the laminate of the present invention are metal. Therefore, for example, in an electrical / electronic device, various members or parts (for example, optical members) are used for attaching (attaching) a predetermined part (for example, a housing) to a member for electrical / electronic devices, In particular, it is useful as a thermal diffusion shock absorbing sheet.

The optical member that can be mounted (mounted) using the laminate of the present invention is the same as the optical member that can be mounted using the foamed sheet of the present invention.

[Electrical and electronic equipment]
The electrical / electronic device of the present invention uses the foamed sheet or laminate of the present invention. Such an electric / electronic device is, for example, an electric / electronic device provided with a display member, and the foam sheet or laminate is sandwiched between the casing of the electric or electronic device and the display member. An electric / electronic device having a structured structure is included. Examples of the electric / electronic devices include mobile communication devices such as so-called “mobile phones”, “smartphones”, and “portable information terminals”.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “%” representing the content means% by weight. In addition, all the compounding parts (parts by weight) are values in terms of solid content (non-volatile content).

Example 1
100 parts by weight of acrylic emulsion solution (solid content 55%, ethyl acrylate-butyl acrylate-acrylonitrile copolymer (weight ratio 45: 48: 7)), fatty acid ammonium surfactant (aqueous dispersion of ammonium stearate, 3 parts by weight of solid content 33%), oxazoline crosslinking agent (Epocross WS-500, manufactured by Nippon Shokubai Co., Ltd., solid content 39%) 0.35 parts by weight, benzotriazole sodium salt (solid content 40%) 1 part by weight, poly Stir and mix 0.8 parts by weight of acrylic thickener (ethyl acrylate-acrylic acid copolymer (acrylic acid 20% by weight), solid content 28.7%) with Disper ("Robomix" Primix) And foamed. This foamed composition was applied onto a release-treated PET (polyethylene terephthalate) film (thickness: 38 μm, trade name “MRF # 38” manufactured by Mitsubishi Plastics), 70 ° C. for 4.5 minutes, and 140 ° C. It was dried for 4.5 minutes to obtain a foam (foamed sheet) having an open cell structure having a thickness of 130 μm, a density of 0.29 g / cm ³ and an average cell diameter of 85 μm.

Example 2
The same operation as in Example 1 was carried out except that the amount of benzotriazole sodium salt (solid content 40%) was 1.5 parts by weight to obtain a foam (foamed sheet) having an open cell structure having a thickness of 130 μm. . The foam had a density of 0.3 g / cm ³ and an average cell diameter of 80 μm.

Example 3
The same operation as in Example 1 was carried out except that the amount of benzotriazole sodium salt (solid content 40%) was changed to 0.5 parts by weight to obtain a foam (foamed sheet) having an open cell structure having a thickness of 130 μm. . The foam had a density of 0.38 g / cm ³ and an average cell diameter of 70 μm.

Comparative Example 1
Except that benzotriazole sodium salt (solid content 40%) was not used at all, the same operation as in Example 1 was carried out to obtain a foam (foamed sheet) having an open cell structure of 130 μm in thickness. The foam had a density of 0.43 g / cm ³ and an average cell diameter of 72 μm.

<Evaluation>
The following evaluation was performed about the foam (foamed sheet) obtained by the Example and the comparative example. The results are shown in Table 1. In Table 1, the numerical value of each component is a weight part in terms of solid content (nonvolatile content).

(Average cell diameter)
An average cell diameter (μm) was obtained by capturing an enlarged image of the foam cross section with a low vacuum scanning electron microscope (“S-3400N scanning electron microscope” manufactured by Hitachi High-Tech Science Systems) and analyzing the image. The number of bubbles analyzed is about 10 to 20.

(density)
A foam (foamed sheet) is punched with a 100 mm × 100 mm punching blade mold, and the dimensions of the punched sample are measured. Further, the thickness is measured with a 1/100 dial gauge having a measurement terminal diameter (φ) of 20 mm. The volume of the foam was calculated from these values.
Next, the weight of the foam is measured with an upper pan balance having a minimum scale of 0.01 g or more. From these values, the density (g / cm ³ ) of the foam was calculated.

(Dynamic viscoelasticity)
A temperature dispersibility test was performed at an angular frequency of 1 rad / s in a film tension measurement mode of a viscoelasticity measurement apparatus (“ARES2KFRTN1-FCO” manufactured by TA Instruments Japan). The peak top temperature (° C.) and strength (maximum value) of loss tangent (tan δ), which is the ratio of storage elastic modulus E ′ and loss elastic modulus E ″ at that time, were measured.
In the column of “tan δ temperature” in Table 1, the peak top temperature (° C.) of the loss tangent (tan δ) of the foam is described, and in the “tan δ maximum value” column, the strength (maximum value) of the peak top is indicated. Described.

(Initial elastic modulus)
The initial elastic modulus (N / mm ² ) calculated from the slope at 10% strain in a tensile test at a tensile speed of 300 mm / min in a 23 ° C. environment was evaluated.

(Adhesive strength)
An adhesive tape (No. 31B, manufactured by Nitto Denko Corporation) was bonded to one surface of the foam (foamed sheet; a release sheet laminated on one side) obtained in each Example and each Comparative Example. This was cut into a size of 20 mm × 100 mm to obtain an evaluation sample. The release sheet was peeled off, the other surface of the foam was attached to a copper foil as an adherend at 25 ° C., and a 5 Kg roller was reciprocated once for pressure bonding. This was left for a predetermined time in each temperature environment, then taken out, left for 2 hours at room temperature, and then subjected to a peel test under the conditions of a peel angle of 180 ° and a tensile speed of 300 mm / min. Force) (N / 20 mm).

(Copper corrosion test)
The foam (foamed sheet) obtained in each Example and each Comparative Example was cut into 52 mm × 52 mm, and bonded to the surface of a 50 mm × 50 mm copper foil using a hand roller, and both sides were acrylic plates (67 mm × 67 mm) × 2 mm (thickness)) and fixed with clips (see FIG. 1). (I) room temperature, (ii) 85 ° C, and (iii) 60 ° C / 95% RH. The sample was taken out after 125 hours, the degree of contamination of the contact surface with the copper foil foam was visually confirmed, and evaluated according to the following criteria. For reference, only the copper foil was allowed to stand in each of the above environments, taken out after 125 hours, the surface of the copper foil was visually observed, and evaluated according to the following criteria. Even if the evaluation is “Δ”, it is practical depending on the application.
○: No change in copper foil △: Copper was slightly corroded ×: Copper was severely corroded and the copper foil surface was discolored

The foam and the foam sheet of the present invention are used for attaching (attaching) various members or parts (for example, optical members) to a predetermined part (for example, a housing) in an electric / electronic device. -It is useful as a sheet for electronic equipment, especially as an impact absorbing sheet. Since the foam and foam sheet of the present invention are excellent in adhesion to metal and corrosion resistance, the member (adhered body) on at least one surface side of the foam sheet is a metal member (for example, copper foil, aluminum foil). , Gold foil, metal foil such as silver foil, etc.).

1 Test piece (foamed sheet)
2 Copper foil 3 Acrylic plate 4 Clip

Claims (17)

1. A foam formed from a thermoplastic resin composition containing a thermoplastic resin (a) and an azole ring-containing compound (b).
2. The foam according to claim 1, wherein the thermoplastic resin composition further contains at least one surfactant.
3. The foam according to claim 1 or 2, wherein the thermoplastic resin (a) is at least one polymer selected from the group consisting of acrylic polymers, rubbers, urethane polymers, and ethylene-vinyl acetate copolymers. .
4. The foam according to any one of claims 1 to 3, wherein the azole ring-containing compound is at least one compound selected from a benzotriazole-based compound and a benzothiazole-based compound.
5. The content of the azole ring-containing compound (b) in the thermoplastic resin composition is 0.2 to 5 parts by weight with respect to 100 parts by weight of the thermoplastic resin (a). 2. The foam according to item 1.
6. The foam according to any one of claims 1 to 5, wherein the thermoplastic resin composition is a water-dispersed thermoplastic resin composition.
7. Loss tangent (tan δ) which is a ratio of storage elastic modulus and loss elastic modulus at a density of 0.2 to 0.7 g / cm ³ , an average cell diameter of 10 to 150 μm, and an angular frequency of 1 rad / s in dynamic viscoelasticity measurement. The foam according to any one of claims 1 to 6, which has a peak top in a range of from -30 ° C to 30 ° C.
8. The foam according to claim 7, wherein the maximum value of the loss tangent (tan δ) in the range of -30 ° C to 30 ° C is 0.2 or more.
9. The foam according to any one of claims 1 to 8, which has an initial elastic modulus of 5 N / mm ² or less in a tensile test at a tensile speed of 300 mm / min in a 23 ° C environment.
10. A foam sheet comprising the foam according to any one of claims 1 to 9.
11. The foam sheet according to claim 10, wherein the thickness is 30 to 500 µm.
12. The foamed sheet according to claim 10 or 11, wherein the adhesive strength to the copper foil (peeling angle 180 °, tensile speed 300 m / min) after being bonded to the copper foil and left at 80 ° C for 1 day is 2 N / 20 mm or more.
13. Based on the step A of mechanically foaming a water-dispersed thermoplastic resin composition containing the thermoplastic resin (a) and the azole ring-containing compound (b), and the water-dispersed resin composition mechanically foamed The foamed sheet according to any one of claims 10 to 12, which is formed through a step B of coating on a material and drying.
14. The foam sheet according to any one of claims 10 to 13, which is used as an impact absorbing sheet for electrical and electronic equipment.
15. 15. A laminate of the foam sheet according to any one of claims 10 to 14 and a heat conductive layer.
16. An electric / electronic device using the foam sheet according to any one of claims 10 to 14 or the laminate according to claim 15.
17. An electric / electronic device provided with a display member, wherein the foam sheet according to any one of claims 10 to 14 or the laminate according to claim 15 comprises a casing of the electric or electronic device, the display member, The electric / electronic device according to claim 16, having a structure sandwiched between the two.

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