Adhesive composition, film-shaped adhesive, and multilayer film

Abstract

Provided is an adhesive composition that provides high adhesion durability even in a high-humidity atmosphere or in water. An adhesive composition according to the present invention is characterized by: containing an acid-modified polyolefin (A) obtained by graft-modifying 100 parts by mass of a polyolefin (a1) with 0.2-5 parts by mass of an acid compound (a2); and having a storage elastic modulus of 130-330 MPa at 23ºC, as measured using a rheometer, and a yield elastic modulus of 30-120 MPa at 23ºC in a tensile test.

Description

Technical Field

[0001] The present invention relates to an adhesive composition that can be suitably used for bonding various parts, a film-shaped adhesive formed by processing the adhesive composition into a film shape, and a multilayer film using the film-shaped adhesive.

Background Art

[0002] Polyolefins represented by polypropylene are lightweight and easy to mold, and have excellent chemical stability such as water resistance, oil resistance, acid resistance, and alkali resistance. For this reason, polyolefins are processed into molded products, sheets, or films as hot melt adhesives and used for bonding various parts. The merit of using thermoplastic polyolefins as adhesives is that, in addition to the above characteristics, the bonding operation is easy and bonding can be performed in a short time, which has a particularly great effect in industrial manufacturing. Furthermore, polyolefins have extremely high storage stability, low toxicity, and low fire hazard, making them easy to manage.

[0003] Polyolefins are highly hydrophobic resins and have low adhesiveness to inorganic substances such as metals and glass as they are. In order to bond inorganic substances, polyolefins with hydrophilic groups introduced are usually used. As methods for introducing hydrophilic groups, a method of copolymerizing a monomer having a hydrophilic group with an olefin monomer and a method of graft-modifying polyolefin with a monomer having a hydrophilic group are known. In the case of propylene, for which copolymerization of a monomer having a hydrophilic group is difficult, the latter method is often adopted. By using a carboxylic acid or carboxylic anhydride as a monomer having a hydrophilic group and grafting the carboxylic acid or carboxylic anhydride onto polypropylene, so-called acid modification, the adhesion of polypropylene to inorganic substances can be enhanced. The adhesion of inorganic substances by acid-modified polyolefins is also described in prior art documents. For example, Patent Document 1 describes acid-modified polypropylene as an adhesive for bonding metals and nylon-based resins.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-109613 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] However, even when a bonded body using an acid-modified polyolefin with an inorganic substance such as metal or glass as an adherend is produced, in an environment where it is in continuous or intermittent contact with moisture, there has been a problem that the adhesive durability is low. This is due to the gradual intrusion of moisture into the adhesive interface, causing the adhesive surface of the bonded body to peel off due to moisture. In particular, when the bonded body is immersed in water and kept in a state where peeling stress is applied for a long time, the inorganic substance easily peels off from the acid-modified polyolefin. Thus, the low adhesive durability in a high-humidity atmosphere and in water is one of the problems of the acid-modified polyolefin that remains unsolved. Patent Document 1, which describes the above-mentioned acid-modified polypropylene, does not mention anything about the adhesiveness of the acid-modified polypropylene when the bonded part is in contact with moisture for a long time.

[0006] As one solution to this problem, there is a method of reducing the amount of acid modification and keeping the adhesive interface hydrophobic, but the problem is that when the amount of acid modification is lowered, the adhesive strength of the acid-modified polyolefin decreases. It has been difficult to achieve both hydrophobicization by reducing the amount of acid modification and the adhesive strength of the acid-modified polyolefin, and an acid-modified polyolefin having sufficient adhesive durability in a high-humidity atmosphere and in water has not been obtained. An object of one embodiment of the present invention is to provide an adhesive composition having high adhesive strength and high adhesive durability in a wide temperature range from low temperature to high temperature, as well as in a high-humidity atmosphere and in water. [Means for Solving the Problems]

[0007] In order to solve the above problems of the polyolefin, the present inventors have variously studied methods for enhancing the adhesive durability to inorganic substances such as metal and glass in water, and have completed the present invention.

[0008] Means for solving the above problems include the following aspects. [1] An acid-modified polyolefin (A) graft-modified with 0.2 to 5 parts by mass of an acid compound (a2) with respect to 100 parts by mass of a polyolefin (a1), The acid compound (a2) is selected from the group consisting of unsaturated carboxylic acids, unsaturated carboxylic acid anhydrides, and combinations thereof, The polyolefin (a1) is selected from the group consisting of polymer blends of polyethylene and polypropylene, propylene-ethylene copolymers, and combinations thereof, The mass ratio (ethylene unit / propylene unit) of the ethylene unit to the propylene unit contained in the polyolefin (a1) is in the range of 15 / 85 to 35 / 65, An adhesive composition having a storage elastic modulus at 23°C measured by a rheometer of 130 to 330 MPa and a yield elastic modulus at 23°C in a tensile test of 30 to 120 MPa. [2] The adhesive composition according to [1], wherein the content of the acid-modified polyolefin (A) is 60% by mass or more. [3] The adhesive composition according to [1] or [2], having a storage elastic modulus at 23°C measured by a rheometer of 150 to 300 MPa and a yield elastic modulus at 23°C in a tensile test of 50 to 100 MPa. [4] The adhesive composition according to any one of [1] to [3], having a tensile fracture strain at 23°C and -10°C of 200% or more, respectively. [5] The adhesive composition according to any one of [1] to [4], having a tensile yield strain at 23°C of 11% or more. [6] A film-like adhesive having a thickness of 10 to 300 μm, comprising the adhesive composition according to any one of [1] to [5]. [7] A multilayer film having a base material layer and a surface layer laminated on the base material layer, wherein the base material layer contains a heat-resistant resin having a softening temperature of 130°C or higher and has a thickness of 50 to 300 μm, and the surface layer is the film-like adhesive according to [6] and has a thickness of 10 to 100 μm. [Effect of the Invention]

[0009] According to the present invention, it is possible to provide an adhesive composition that gives high adhesive strength and high adhesive durability even in a high humidity atmosphere and in water over a wide temperature range from low temperature to high temperature.

Brief Description of the Drawings

[0010]

Figure 1

Embodiments for Carrying Out the Invention

[0011] The adhesive composition contains an acid-modified polyolefin (A).

[0012] The acid-modified polyolefin (A) is a polyolefin in which a polyolefin (a1), particularly an unmodified polyolefin (a1), is graft-modified with an acid compound (a2) selected from the group consisting of unsaturated carboxylic acids, unsaturated carboxylic acid anhydrides, and combinations thereof. Here, the acid-modified polyolefin (A) may contain a polyolefin (a1) that is not partially graft-modified with the acid compound (a2). That is, the acid-modified polyolefin (A) may be a polyolefin composed of a polyolefin (a1) and a polyolefin (a1) graft-modified with an acid compound (a2) selected from the group consisting of unsaturated carboxylic acids, unsaturated carboxylic acid anhydrides, and combinations thereof. The graft-modified polyolefin generally has a polyolefin chain based on the polyolefin (a1) and a graft chain that is a polymer of the acid compound (a2).

[0013] The polyolefin (a1) used as a raw material for the acid-modified polyolefin (A) is selected from the group consisting of polymer blends of polyethylene and polypropylene, ethylene-propylene copolymers, and combinations thereof.

[0014] Polyethylene is a polymer containing ethylene units as the main component, and it may be a homopolymer or a copolymer. The content of ethylene units in polyethylene is preferably 50% by mass or more, more preferably 70% by mass or more. Specific examples of polyethylene include homopolymers such as low-density polyethylene, high-density polyethylene, and linear low-density polyethylene, copolymers such as ethylene-diene monomer copolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic ester copolymers, and ethylene-methacrylic ester copolymers, and halogenated derivatives such as chlorinated polyethylene.

[0015] Polypropylene is a polymer containing propylene units as the main component, and it may be a homopolymer or a copolymer. The content of propylene units in polypropylene is preferably 50% by mass or more, more preferably 70% by mass or more. Specific examples of polypropylene include homopolymers such as amorphous polypropylene and crystalline polypropylene, copolymers such as propylene-diene monomer copolymers, and halogenated derivatives such as chlorinated polypropylene.

[0016] An ethylene-propylene copolymer is a polymer containing ethylene units and propylene units, and it may be composed only of ethylene units and propylene units, or may further contain other monomer units in addition to ethylene units and propylene units. Examples of ethylene-propylene copolymers containing other monomer units include ethylene-propylene-diene monomer copolymers. The total amount of ethylene units and propylene units in the ethylene-propylene copolymer is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass.

[0017] Polyolefin (a1) includes, in addition to physical blends composed of multiple components of these resins, reaction blends in which functional groups are reacted between different polymers in a molding machine, graft copolymers and block copolymers composed of multiple segments, and compositions in which physical blends using these as compatibilizers are microdispersed.

[0018] In all monomer units contained in the polyolefin (a1), the total amount of ethylene units and propylene units is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass.

[0019] The mass ratio of ethylene units to propylene units (ethylene units / propylene units) contained in the polyolefin (a1) is 15 / 85 or more, preferably 20 / 80 or more. The mass ratio of ethylene units to propylene units (ethylene units / propylene units) contained in the polyolefin (a1) is 35 / 65 or less, preferably 30 / 70 or less. When the polyolefin (a1) is a polymer blend of polyethylene and polypropylene, the "mass ratio of ethylene units to propylene units contained in the polyolefin (a1)" means the mass ratio of ethylene units to propylene units in all monomer units contained in polyethylene and polypropylene.

[0020] The mass ratio of ethylene units and propylene units is determined from the absorbance ratio of the characteristic absorption of polyethylene (719 cm -1 ) and the characteristic absorption of polypropylene (1167 cm -1 ) in the IR spectrum. Specifically, a calibration curve for converting the absorbance ratio of ethylene units and propylene units into a mass ratio is used. The calibration curve can be created by blending commercially available polyethylene and polypropylene in various ratios and plotting the blending ratio and the absorbance ratio.

[0021] When the polyolefin (a1) is a polymer blend of polyethylene and polypropylene, the mass ratio of polyethylene to polypropylene (polyethylene / polypropylene) is preferably 15 / 85 or more, more preferably 20 / 80 or more. When it is a polymer blend of polyethylene and polypropylene, the mass ratio of polyethylene to polypropylene (polyethylene / polypropylene) is preferably 35 / 65 or less, more preferably 30 / 70 or less.

[0022] By setting the mass ratio of ethylene units to propylene units, or the mass ratio of polyethylene to polypropylene, within the range shown above, it is possible to achieve both high-temperature and low-temperature adhesion durability.

[0023] The polyolefin (a1) may contain monomer units other than ethylene units and propylene units. Examples of monomers that form monomer units other than ethylene units and propylene units include α-olefins such as 1-butene, 1-pentene, 1-hexene, 4-methylpentene-1, diene monomers such as butadiene, isoprene, chloroprene, unsaturated carboxylic acids and their derivatives such as vinyl acetate, acrylic esters, acrylic acid, methacrylic acid, methacrylic esters, and aromatic vinyl compounds such as styrene. The content of monomer units other than ethylene units and propylene units in the polyolefin (a1) is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less. When the content of monomer units other than ethylene units and propylene units is within such a range, the properties of the polyolefin such as water resistance, chemical resistance, and durability are enhanced, and it becomes possible to produce the polyolefin at low cost.

[0024] Examples of the production method of the polyolefin (a1) include known production methods using a polymerization catalyst. Examples of the polymerization catalyst include Ziegler catalysts and metallocene catalysts, and examples of the polymerization method include slurry polymerization and gas-phase polymerization. Impact-resistant polypropylene, which is referred to as a polypropylene block polymer, is substantially a mixture of polypropylene and a propylene-ethylene random copolymer, and can be produced by a process consisting of a first step of obtaining a homopolymer of propylene and a second step of obtaining a propylene-ethylene random copolymer.

[0025] The acid compound (a2) is selected from the group consisting of unsaturated carboxylic acids, unsaturated carboxylic acid anhydrides, and combinations thereof.

[0026] An unsaturated carboxylic acid is a compound having an ethylenic double bond and a carboxylic acid group in the same molecule, and examples thereof include various unsaturated monocarboxylic acids and unsaturated dicarboxylic acids.

[0027] Specific examples of the unsaturated monocarboxylic acid include acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid and the like.

[0028] Specific examples of the unsaturated dicarboxylic acid include maleic acid, fumaric acid, itaconic acid, citraconic acid, nadic acid, endic acid and the like.

[0029] An unsaturated carboxylic anhydride is a compound having an ethylenic double bond and a carboxylic anhydride group in the same molecule, and examples thereof include the acid anhydrides of the above-mentioned unsaturated dicarboxylic acids.

[0030] Specific examples of the acid anhydrides of the unsaturated dicarboxylic acid include maleic anhydride, fumaric anhydride, itaconic anhydride, citraconic anhydride, nadic anhydride, endic anhydride and the like.

[0031] Among these, maleic acid and maleic anhydride are preferably used because of their high modification effect, and maleic anhydride is particularly preferably used.

[0032] These acid compounds (a2) may be used alone or in combination of two or more.

[0033] As the method of graft modification, a known method can be adopted. For example, in the presence of a radical polymerization initiator such as an organic peroxide or an aliphatic azo compound, a method of subjecting the acid compound (a2) to a graft reaction with the polyolefin (a1) in a molten state or a solution state can be mentioned.

[0034] The temperature of the graft reaction is 80 to 160 ° C when reacting in a solution state, and the reaction in a molten state When causing the reaction, a temperature of 150 to 300°C is preferable. In each of the solution state and the molten state, the reaction rate becomes high at a temperature equal to or higher than the lower limit value of the above reaction temperature range, the decrease in the molecular weight of the resin is small at a temperature equal to or lower than the upper limit value of the above reaction temperature range, and the mechanical strength of the obtained acid-modified polyolefin (A) can be maintained.

[0035] The radical polymerization initiator to be used may be selected from commercially available organic peroxides in consideration of the reaction temperature and the like.

[0036] When a part of the acid compound (a2) used for the graft modification is unreacted, in order to suppress the adverse effect on the adhesive strength, it is preferable to remove the unreacted acid compound (a2) by a known method such as distillation under reduced pressure. Further, the acid-modified polyolefin (A) may contain a part of an unmodified polyolefin (a1) such as polyethylene, polypropylene, or an ethylene-propylene copolymer.

[0037] In the graft modification, the amount of the acid compound (a2) grafted onto the polyolefin (a1) is 0.2 parts by mass or more, preferably 0.4 parts by mass or more, based on 100 parts by mass of the polyolefin (a1) before acid modification. When the amount of the acid compound grafted is in such a range, the adhesiveness of the adhesive composition can be enhanced.

[0038] In the graft modification, the amount of the acid compound (a2) grafted onto the acid-modified polyolefin (A) is 5 parts by mass or less, preferably 2 parts by mass or less, based on 100 parts by mass of the polyolefin (a1). When the amount of the acid compound (a2) grafted is in such a range, the adhesion durability of the adhesive composition in water can be enhanced.

[0039] The acid value of the acid-modified polyolefin (A) is preferably 0.041 meq / g or more, more preferably 0.082 meq / g or more. The acid value of the acid-modified olefin (A) is preferably 1.02 meq / g or less, more preferably 0.408 meq / g or less.

[0040] The melting point of the acid-modified polyolefin (A) is preferably 130°C or higher, more preferably 135°C or higher. When the melting point of the acid-modified polyolefin (A) is within such a range, the heat resistance of the adhesive composition and the adhesive strength at high temperatures are improved. The melting point of the acid-modified polyolefin (A) is preferably 150°C or lower, more preferably 145°C or lower. When the melting point of the acid-modified polyolefin (A) is within such a range, the adhesion durability of the adhesive composition at low temperatures is improved.

[0041] In the present invention, the melting point means the temperature at the peak of the endothermic peak that occurs in the process of heating from 0°C to 200°C at a rate of 10°C per minute after once holding at 180°C for several minutes and then cooling to 0°C using a differential scanning calorimeter (DSC).

[0042] The melt flow rate of the acid-modified polyolefin (A) is preferably 3 g / 10 min or higher, more preferably 7 g / 10 min or higher. The melt flow rate of the acid-modified polyolefin (A) is preferably 50 g / 10 min or lower, more preferably 30 g / 10 min or lower.

[0043] In the present invention, the melt flow rate means the value measured at a resin temperature of 230°C and a load of 2.16 kg in accordance with JIS K7210:2014.

[0044] The content of the acid-modified polyolefin (A) in the adhesive composition is preferably 60% by mass or higher, more preferably 70% by mass or higher, particularly preferably 80% by mass or higher, and may be 100% by mass.

[0045] In the adhesive composition, polymers other than the acid-modified polyolefin (A) (hereinafter referred to as other polymers) can be added for the purpose of improving adhesion strength at low temperatures, adhesion durability, moldability stability, and miscibility between resins. Examples of other polymers include styrene-based block copolymers such as ethylene-propylene rubber, styrene-butadiene-styrene block copolymer and its hydrogenated product, styrene-isoprene-styrene block copolymer and its hydrogenated product, and styrene-isobutylene-styrene block copolymer and its hydrogenated product.

[0046] When using other polymers, the lower limit of the content of other polymers in the adhesive composition is preferably 1% by mass or more, more preferably 2% by mass or more, and particularly preferably 3% by mass or more. When the addition amount of other polymers is in such a range, the improvement effect by other polymers is enhanced.

[0047] When using other polymers, the upper limit of the content of other polymers in the adhesive composition is preferably 20% by mass or less, more preferably 15% by mass or less, and particularly preferably 10% by mass or less. When the addition amount of other polymers is in such a range, the adhesive composition can obtain high heat resistance and high adhesion strength at high temperatures.

[0048] The adhesive composition may further contain additives selected from the group consisting of antioxidants, ultraviolet absorbers, fillers, reinforcing fibers, release agents, processing aids, flame retardants, plasticizers, nucleating agents, antistatic agents, pigments, dyes, foaming agents, and combinations thereof.

[0049] The storage modulus at 23°C measured by a rheometer for the adhesive composition is 130 MPa or more, preferably 150 MPa or more, more preferably 175 MPa or more. When the storage modulus is within such a range, the adhesive strength of the adhesive composition at high temperatures is improved. The storage modulus at 23°C for the adhesive composition is 330 MPa or less, preferably 300 MPa or less, more preferably 200 MPa or less. When the storage modulus is within such a range, the adhesive strength of the adhesive composition at low temperatures is improved.

[0050] Here, the measurement conditions of the rheometer are a frequency of 1 Hz, a strain range of 0.01 to 0.2%, and a temperature increase rate of 2°C / min. The storage modulus described in this specification is the storage modulus at 23°C when the temperature is increased from -50°C to 180°C under these conditions.

[0051] As an example of a method for adjusting the storage modulus to an appropriate range, it is possible to adjust the blending amount of amorphous polyolefins such as ethylene-propylene rubber and styrene block copolymers. By increasing these, the storage modulus can be decreased.

[0052] The yield modulus at 23°C in the tensile test of the adhesive composition is 30 MPa or more, preferably 50 MPa or more, more preferably 60 MPa or more.

[0053] When the yield modulus is within such a range, the adhesive strength of the adhesive composition at high temperatures is improved. The yield modulus at 23°C in the tensile test of the adhesive composition is 120 MPa or less, preferably 100 MPa or less, more preferably 80 MPa or less. When the yield modulus is within such a range, the adhesive strength of the adhesive composition at low temperatures is improved.

[0054] Here, the measurement conditions of the tensile test are a gauge length of 35 mm at the start of the test and a tensile speed of 50 mm / min. The yield elastic modulus described in this specification is the yield elastic modulus measured using a commercially available tensile testing machine under these conditions with a strip-shaped test piece having a thickness of 100 to 300 μm and a size of 10 mm × 60 mm. The strip-shaped test piece with a thickness of 100 to 300 μm and a size of 10 mm × 60 mm can be produced by press molding or the like. Note that the yield elastic modulus means the elastic modulus obtained by dividing the stress (yield stress) at the yield point (the point where the stress shows a maximum value) by the strain (yield strain).

[0055] As an example of a method for adjusting the yield elastic modulus to an appropriate range, adjusting the blending amount of an amorphous polyolefin such as ethylene-propylene rubber or a styrene block copolymer can be mentioned. By increasing these, the yield elastic modulus can be lowered.

[0056] The tensile fracture strain at 23°C and -10°C in the tensile test of the adhesive composition is preferably 200% or more in both cases. When the tensile fracture strain at 23°C and -10°C in the tensile test is 200% or more, the adhesive composition has excellent adhesion stability at low temperatures. The tensile test is the same as that conducted in the measurement of the yield elastic modulus described above. The upper limit of the tensile fracture strain is not particularly limited. For example, the tensile fracture strain at 23°C and -10°C in the tensile test of the adhesive composition may be 500% or less in both cases.

[0057] The yield strain at 23°C in the tensile test of the adhesive composition is preferably 11% or more, more preferably 12% or more, and particularly preferably 15% or more. When the yield strain at 23°C is within such a range, the adhesive composition has excellent adhesive strength at low temperatures. The tensile test is the same as that conducted in the measurement of the yield elastic modulus described above. The upper limit of the yield strain is not particularly limited. For example, the yield strain at 23°C in the tensile test of the adhesive composition may be 30% or less.

[0058] The adhesive composition can be formed into a film and used as a film-shaped hot melt adhesive. By using the film-shaped hot melt adhesive, it is possible to dramatically improve the productivity of the adhesion / sealing process, and a large number of bonded bodies with fine, precise, and complex fusion sites can be manufactured in a short time and at low cost.

[0059] Normally, the film-shaped hot melt adhesive consists of an adhesive composition, but it may contain other components such as moisture.

[0060] The content of the adhesive composition in the film-shaped hot melt adhesive is preferably 50% by mass or more, more preferably 70% by mass or more, and particularly preferably 90% by mass or more.

[0061] The thickness of the film-shaped hot melt adhesive is preferably 10 μm or more, more preferably 20 μm or more. When the thickness of the film-shaped hot melt adhesive is within such a range, the film-shaped hot melt adhesive has high adhesiveness. The thickness of the film-shaped hot melt adhesive is preferably 300 μm or less, more preferably 200 μm or less. When the thickness of the film-shaped hot melt adhesive is within such a range, the film-shaped hot melt adhesive can exhibit excellent adhesive performance, productivity, and economy. In addition, when the film-shaped hot melt adhesive is pressure-bonded to the adherend, the extrusion of the film-shaped hot melt adhesive can be prevented.

[0062] If the film-shaped hot melt adhesive is used as the surface layer of a multilayer film, it is also possible to obtain a higher-performance and higher-functional adhesion / sealing member.

[0063] In this case, a multilayer film including a surface layer formed of the film-shaped hot melt adhesive and a base material layer containing a heat-resistant resin is particularly preferably used.

[0064] The surface layer is a layer laminated on the base material layer, and it may be formed only on one surface of the base material layer or on both surfaces of the base material layer. Also, a primer layer may be provided between the surface layer and the base material layer. Although not particularly limited, the heat-resistant resin preferably has a softening temperature of 130 °C or higher. When the softening temperature of the heat-resistant resin is 130 °C or higher, the heat resistance, rigidity, and dimensional stability of the multilayer film are improved. Here, the softening temperature is the temperature at which the storage elastic modulus measured with a rheometer becomes 10 MPa or less. The measurement conditions of the rheometer are the same as those used in the measurement of the storage elastic modulus described above. The content of the heat-resistant resin in the base material layer is not particularly limited, but is preferably 50% by mass or more, more preferably 70% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass.

[0065] Specific examples of the heat-resistant resin include polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and polyarylate; polyolefin polymers such as cyclic olefin polymer (COP), cycloolefin copolymer, and methylpentene polymer (TPX); polyamide resins such as nylon-6, nylon-6,6, and aromatic polyamide; polyether amide, polyamideimide, polyimide, polyetheretherketone, polyetherketone, polyketone, polysulfone, polyethersulfone, polyphenylsulfone, polyphenylene sulfide, polyphenylene ether, an alloy composed of polyphenylene ether and polystyrene, an alloy composed of polyphenylene ether and polypropylene, an alloy composed of polyphenylene ether and polyamide, an alloy composed of polyphenylene ether and cyclic olefin polymer or cycloolefin copolymer, polyacetal, polycarbonate, etc. Among these, from the viewpoints of heat resistance, rigidity, and dimensional stability, polyethylene naphthalate, cyclic olefin polymer, cycloolefin copolymer, polyphenylene ether, and / or an alloy containing 50% or more of polyamide resin is preferably used.

[0066] The thickness of the surface layer is the same as that of the film-like hot melt adhesive described above, but 10 to 100 μm is particularly preferred. By setting the thickness of the surface layer to 10 μm or more, the multi-layer film can have good adhesiveness. By setting the thickness of the surface layer to 100 μm or less, the multi-layer film can have good heat resistance and mechanical strength.

[0067] The thickness of the base material layer is particularly preferably 50 to 300 μm. By setting the thickness of the base material layer to 50 μm or more, the multi-layer film can have good heat resistance, rigidity, and dimensional stability. By setting the thickness of the base material layer to 300 μm or less, the manufacturing cost can be reduced, and appropriate flexibility can be imparted to the multi-layer film.

[0068] A film-like hot melt adhesive or a multi-layer film using the same can be adhered to various adherends such as metal, glass, and plastic to produce a joined body.

[0069] The metal used as the adherend may be a generally known metal plate, metal flat plate, or metal foil, and iron, copper, aluminum, lead, zinc, titanium, chromium, stainless steel, etc. can be used. Among these, iron, aluminum, titanium, and stainless steel are particularly preferred.

[0070] The adhesive composition can be produced by melt-kneading an acid-modified polyolefin (A) and other components as necessary using an extruder, Banbury mixer, hot roll, etc., cooling and solidifying the strand extruded from the nozzle hole of the die head with water or the like while pulling it, and cutting it into pellets. The temperature of the melt-kneading is preferably 150 to 270 °C, more preferably 170 to 250 °C, the kneading time is usually 0.5 to 20 minutes, and preferably 1 to 15 minutes.

[0071] The adhesive composition thus obtained can be made into molded articles of various shapes according to the intended use by a conventionally known method, such as compression molding, injection molding, extrusion molding, multilayer extrusion molding, profile extrusion molding, or blow molding. When producing a resin sheet or film suitable for adhesion or sealing applications, it may be melted in a single-screw extruder and then formed into a sheet of a predetermined thickness through a roll, cooled, and wound up.

Examples

[0072] Examples and comparative examples are shown below to more specifically explain the present invention. Unless otherwise specified, "parts" means parts by mass and "%" means mass % hereinafter. Also, unless otherwise specified, "PP" means polypropylene, "PE" means polyethylene, and "MAH" means maleic anhydride.

[0073] <Calibration curve creation> A commercially available polyethylene resin (P9210 manufactured by Kyoeisha Polyethylene Co., Ltd.) and a polypropylene resin (Waymax MFX3 manufactured by Nippon Polypro Co., Ltd.) were melt-kneaded in an extruder at various compounding ratios, and the resulting resin mixture was molded using a tabletop press molding machine to produce a resin sheet with a thickness of about 2 mm.

[0074] Using Spectrum100 manufactured by PerkinElmer, an IR spectrum was obtained from the cut surface of the resin sheet by the total reflection absorption method (ATR method). The PE absorbance ratio was determined from the absorbances at 719 cm -1 (PE characteristic absorption) and 1167 cm -1 (PP characteristic absorption). A calibration curve was created by plotting this absorbance ratio and the compounding ratio during melt-kneading. The results of the PE compounding ratio and the PE absorbance ratio are shown in Table 1, and the results of the plot are shown in Figure 1.

[0075] Taking measurement errors into account, the number of repetitions was set to 4 or more. The approximate curve of this plot was used as a calibration curve for determining the PE / PP compounding ratio.

[0076]

Table 1

[0077] <Identification of Maleic Anhydride-Modified Polyolefin Maleic anhydride-modified polyolefins A to F mainly composed of polypropylene, polyethylene, ethylene-propylene copolymer, and their maleic anhydride-modified products were prepared.

[0078] Maleic anhydride-modified polyolefins A to F were molded into resin sheets with a thickness of 2 mm, and the IR spectrum was similarly measured using the cross-section as the measurement surface. Based on the obtained IR spectrum, the PE / PP blending ratio was determined using the prepared calibration curve.

[0079] Also, the amount of maleic anhydride contained was quantified by neutralization titration. In the neutralization titration, maleic anhydride-modified polyolefins A to F as samples were heated and dissolved in xylene, and the resulting solution was titrated with an ethanol solution of potassium hydroxide using phenol red as an indicator. The results of the estimated PE / PP blending ratio and the amount of maleic anhydride are shown in Table 2.

[0080]

Table 2

[0081] <Physical Properties of Maleic Anhydride-Modified Polyolefin [Viscoelastic Spectrum] Sheets of maleic anhydride-modified polyolefins A to F with a thickness of about 400 μm prepared using a tabletop press molding machine were cut into a circular shape to prepare test pieces for measuring the viscoelastic spectrum. The viscoelastic spectrum of this test piece was measured using a rheometer MCR301 manufactured by Anton Paar. The measurement conditions were a frequency of 1 Hz, a strain range of 0.01 to 0.2%, a normal force of 0.01 N, and the test piece was heated from -50°C to 180°C at a heating rate of 2°C / min. The storage modulus at 23°C was recorded as an index of the modulus of elasticity. The storage moduli of maleic anhydride-modified polyolefins A to F are shown in Table 3.

[0082] [Tensile Test] From the sheets of maleic anhydride-modified polyolefins A to F with a thickness of 100 to 300 μm produced using a tabletop press molding machine, strip-shaped test pieces with a size of 10 mm × 60 mm were cut out to prepare test pieces for the tensile test. An Instron tensile testing device (Instron 5566A) was used for the tensile testing machine. With the distance between the fixtures set at 35 mm, the tensile test was conducted at a tensile speed of 50 mm / min. The point at which the stress shows a maximum value after passing through the initial elastic region was defined as the yield point. The stress at the yield point was defined as the yield stress, and the strain at the yield point was defined as the yield strain. The strain was calculated with the initial length of the distance between the fixtures set at 35 mm. The elastic modulus obtained by dividing the yield stress by the yield strain was defined as the yield elastic modulus. Table 3 shows the yield stress, yield strain, yield elastic modulus, fracture strain measured at 23°C, and the yield stress and fracture strain measured at -10°C as the mechanical properties of maleic anhydride-modified polyolefins A to F.

[0083] [Melt Flow Rate] The melt flow rate (MFR) was measured in accordance with JIS K7210:2014 using a commercially available melt indexer (G-02 manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a resin temperature of 230°C and a load of 2.16 kg. Table 3 shows the melt flow rates of maleic anhydride-modified polyolefins A to F.

[0084] [Peel Strength] Sheets of maleic anhydride-modified polyolefins A to F with a thickness of 100 to 300 μm were prepared using a tabletop press molding machine. A SUS304 plate with a thickness of 0.1 mm was used as the adherend. Both sides of the sheets of maleic anhydride-modified polyolefins A to F were sandwiched between SUS304 plates and heat-pressed (180°C, 10 seconds, 4 MPa) using a precision press machine to produce a bonded body. This bonded body was cut into strips with a width of 10 mm to obtain test pieces for the peel test. The peel strength of this test piece was measured by a T-peel test. In the T-peel test, an Instron tensile testing device (Instron 5564) was used to peel the SUS304 plate at a tensile speed of 50 mm / min, and the peel force in the stable region was defined as the peel strength (N / 10 mm width). Table 3 shows the peel strengths of maleic anhydride-modified polyolefins A to F.

[0085] [Adhesion Durability in Water] To evaluate the adhesion durability in water, a constant load immersion test was conducted. The same test specimens as those used for measuring the peel strength described above were used in the constant load immersion test. One side of the holding part of the test specimen was fixed to the fixing stand with a wire, and the other side was connected to a weight. The test specimen was suspended into the water together with the weight from the fixing stand installed above the water surface, and a peel load (2 N or 4 N) was applied by the weight in the water. At this time, the time required (falling time) until the SUS304 plate as the adherend was completely separated was measured. The adhesion durability in water was evaluated based on the length of the falling time of the SUS304 plate. Tests were respectively conducted in water at 95 °C as an evaluation of the adhesion durability at high temperature, and in water at 23 °C as an evaluation of the adhesion durability at low temperature. The results of the constant load immersion test of maleic anhydride-modified polyolefins A to F are shown in Table 3.

[0086]

Table 3

[0087] As can be seen from the results in Table 3, maleic anhydride-modified polyolefins C, D, and E have long falling times in both low and high temperatures in terms of peel strength and constant load immersion test, indicating that they are excellent in adhesiveness and adhesion durability in water.

Industrial Applicability

[0088] The adhesive composition of the present invention, as well as the film-shaped adhesive and multilayer film obtained by processing the same, are useful for the adhesion and sealing of metal materials, and are preferably used in applications where the resulting joined body may be continuously or intermittently in contact with moisture.

[0089] For example, electric wires and cables in which a metal conductor or an optical fiber is coated with a resin molded product, automotive mechanism parts, automotive exterior parts, automotive interior parts, power supply molded substrates, light reflectors for light sources, fuel cases for solid methanol fuel cells, heat insulators for metal pipes, heat insulators for vehicles, fuel cell water pipes, decorative molded products, water-cooling tanks, boiler exterior cases, ink peripheral parts and members of printers, water pipes, joints, secondary battery alkaline storage battery tanks, gasket sealing materials for various laminated batteries, and the like can be mentioned.

[0090] This application claims priority based on Japanese Patent Application No. 2020-158485 filed on September 23, 2020, and all of its disclosures are incorporated herein by reference.

Claims

1. An acid-modified polyolefin (A) graft-modified with 0.2 to 5 parts by mass of an acid compound (a2) with respect to 100 parts by mass of a polyolefin (a1), wherein the content of the acid-modified polyolefin (A) is 60% by mass or more, the acid compound (a2) is selected from the group consisting of an unsaturated carboxylic acid, an unsaturated carboxylic anhydride, and combinations thereof, the polyolefin (a1) is selected from the group consisting of a polymer blend of polyethylene and polypropylene, a propylene-ethylene copolymer, and combinations thereof, the mass ratio (ethylene unit / propylene unit) of the ethylene unit and the propylene unit contained in the polyolefin (a1) is in the range of 15 / 85 to 35 / 65, an adhesive composition having a storage elastic modulus at 23°C of 130 to 330 MPa measured by a rheometer under the measurement condition of a frequency of 1 Hz and a yield elastic modulus at 23°C in a tensile test of 30 to 120 MPa.

2. The adhesive composition according to claim 1, having a storage elastic modulus at 23°C of 150 to 300 MPa measured by a rheometer under the measurement condition of a frequency of 1 Hz and a yield elastic modulus at 23°C in a tensile test of 50 to 100 MPa.

3. The adhesive composition according to claim 1 or claim 2, having a tensile fracture strain at 23°C and -10°C of 200% or more, respectively.

4. The adhesive composition according to any one of claims 1 to 3, having a tensile yield strain at 23°C of 11% or more.

5. A film-like adhesive having a thickness of 10 to 300 μm, comprising the adhesive composition according to any one of claims 1 to 4.

6. A multilayer film having a base material layer and a surface layer laminated on the base material layer, wherein the base material layer contains a heat-resistant resin having a softening temperature of 130°C or higher and has a thickness of 50 to 300 μm, and the surface layer is the film-like adhesive according to claim 5 and has a thickness of 10 to 100 μm.

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