Polyolefin adhesive composition

Abstract

Provided is an adhesive composition which does not require a curing process and which exhibits good adhesion and heat resistance between a polyolefin resin substrate and a metal substrate. An adhesive composition containing a modified polyolefin (A) and an olefin-alpha-olefin copolymer (B), (1) containing 15-85 parts by mass of the olefin-alpha-olefin copolymer (B) per 100 parts by mass of the modified polyolefin (A); (2) The olefin / alpha-olefin copolymer (B) has a weight average molecular weight of 200,000 or more. (3) the olefin-alpha-olefin copolymer (B) has a melting point of 80 DEG C or more and 100 DEG C or less; and (4) the weight-average molecular weight of the modified polyolefin (A) < = the weight-average molecular weight of the olefin-alpha-olefin copolymer (B).

Description

TECHNICAL FIELD

[0001] The present application relates to an adhesive composition using a modified polyolefin and an olefin-α-olefin copolymer. Further in detail, it relates to an adhesive composition suitable for bonding of a polyolefin resin substrate and a metal substrate. BACKGROUND

[0002] Metal components are used in the fields of home appliance outer panels, furniture materials, building interior components, electrical and electronic components, and the like. In addition, in order to lighten the components, plastic components, particularly polyolefin resin components, are also used. Conventionally, since it is difficult to bond a high-polar metal substrate and a low-polar polyolefin resin substrate, they are used after being joined by welding, screwing, or the like. On the other hand, in order to improve the efficiency of the component manufacturing process, various adhesive compositions for bonding a metal substrate and a polyolefin resin substrate have been proposed, but since these components are used in various environments, the adhesive is required to have more severe resistance. For example, electrical and electronic components are exposed to a high-temperature environment due to heat generation at the time of charging and discharging, and the like, and thus an adhesive composition that exhibits high adhesive strength even in an environment of around 25°C and 90°C is required.

[0003] As a composition for bonding a polyolefin resin substrate and a metal substrate, for example, in Patent Literature 1, a polyolefin adhesive composition modified with an α,β-unsaturated carboxylic acid, a (meth)acrylate is disclosed. In addition, in Patent Literature 2, an adhesive composition in which an isocyanate curing agent is mixed with an α,β-unsaturated carboxylic acid, a (meth)acrylate-modified polyolefin is disclosed. PRIOR ART DOCUMENTS PATENT LITERATURE

[0004] Patent Literature 1: Japanese Patent Application Laid-Open No. 2020-143181 Patent Literature 2: Japanese Patent No. 6673411 SUMMARY PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] However, in Patent Literature 1, unreacted (meth)acrylate is not taken into consideration, and particularly at high temperatures, high-polar (meth)acrylate is precipitated to the surface, which leads to a decrease in affinity with the polyolefin resin substrate, and thus there is a problem point that the adhesive strength at high temperatures is low. In addition, the heat-curable adhesive described in Patent Literature 2 has a problem that a long maturation time is required in order to complete the curing reaction.

[0006] This invention addresses issues arising from existing technologies. Specifically, the object of this invention is to provide an adhesive composition that exhibits good adhesion and heat resistance to a polyolefin resin substrate and a metal substrate without the need for aging. Furthermore, it provides an adhesive composition that exhibits good adhesive strength even under high-temperature, short-time processing conditions such as injection molding. Further, it provides a laminate comprising a polyolefin resin substrate, an adhesive layer composed of the said adhesive composition, and a metal substrate.

[0007] The inventors conducted in-depth research to solve the aforementioned problems, thus completing this invention. Specifically, this invention comprises the following components. [1] An adhesive composition, characterized in that it contains a modified polyolefin (A) and an olefin-α-olefin copolymer (B), and satisfies all of the following conditions (1) to (4): (1) The olefin-α-olefin copolymer (B) is contained in a ratio of 15 to 85 parts by mass relative to 100 parts by mass of the modified polyolefin (A). (2) The weight average molecular weight of the olefin-α-olefin copolymer (B) is above 200,000; (3) The melting point of the olefin-α-olefin copolymer (B) is above 80℃ and below 100℃; (4) The weight-average molecular weight of the modified polyolefin (A) is less than the weight-average molecular weight of the olefin-α-olefin copolymer (B). [2] According to the adhesive composition described in [1], the modified polyolefin (A) has a weight-average molecular weight of 70,000 or more and less than 200,000. [3] The adhesive composition according to [1] or [2] further contains an organic solvent (C). [4] According to the adhesive composition described in [1] to [3], the modified polyolefin (A) has an acid value of 2 to 50 mg KOH / g. [5] The adhesive composition according to [1] to [4] is used for bonding a polyolefin resin substrate to a metal substrate. [6] A laminate comprising, in sequence, a polyolefin resin substrate, the adhesive composition described in [1] to [5], and a metal substrate. The effects of the invention

[0008] The adhesive composition of the present invention exhibits excellent adhesion to polyolefin resin substrates and metal substrates. Furthermore, due to its heat resistance, it can also be used for bonding at high temperatures without the need for curing treatment. Therefore, it is particularly suitable as an adhesive for injection-molded polyolefin resins and metal substrates. Attached Figure Description

[0009] [Figure 1 Figure 1 FIG. 1 is a cross-sectional view showing an example of a laminate of the present application. Figure 2 Figure 2 FIG. 2 is a view showing a test piece for measuring the adhesive strength of the present application. Figure 3 Figure 3 FIG. 3 is a view showing a state in which the adhesive strength is measured using the test piece.

[0010] In the drawings of the present specification, the scale and the ratio of the length and width, etc. are appropriately changed compared to the actual size for the convenience of easy illustration and understanding of the drawings. Explanation of symbols

[0011] 1 polyolefin resin base material, 2 adhesive composition, 3 metal base material (aluminum plate) DETAILED DESCRIPTION

[0012] The present application will be described in detail below. <Modified polyolefin (A)> The modified polyolefin (A) used in the present application is not limited, and is preferably one obtained by applying modification to at least one of polyethylene, polypropylene, and propylene / α-olefin copolymer. Further, the modified polyolefin (A) is more preferably one obtained by applying modification to polypropylene or propylene / α-olefin copolymer, and is further preferably one obtained by applying modification to propylene / α-olefin copolymer. Further, from the viewpoint of improving the compatibility, the modified polyolefin (A) is particularly preferably one obtained by applying modification to the same resin as the olefin-α-olefin copolymer (B) used. Thereby, the compatibility of the modified polyolefin (A) and the olefin-α-olefin copolymer (B) can be improved, and excellent adhesion can be exhibited.

[0013] The propylene / α-olefin copolymer described above is a copolymer of propylene as a main component and α-olefin. As the α-olefin, one or a plurality of kinds of ethylene, 1-butene, 1-heptene, 1-octene, 4-methyl-1-pentene, vinyl acetate, etc. can be used. From the viewpoint of adhesion and dissolution stability, a copolymer of propylene and 1-butene is particularly preferable. The molar ratio of the propylene component and the α-olefin component in the propylene / α-olefin copolymer is not particularly limited, and the propylene component is preferably 50 mol% or more, and more preferably 70 mol% or more. By making the molar ratio of propylene 50% or more, excellent adhesion to the polyolefin resin base material, particularly to the polypropylene resin base material can be exhibited.

[0014] As the modification of the modified polyolefin (A) used in the present application, acid modification, chlorine modification, hydroxyl modification, etc. can be specifically mentioned. Among these, from the viewpoint of the adhesion of the modified polyolefin (A) to the metal base material and the manufacturing efficiency, acid modification is particularly preferable. ​​​​​

[0015] The modified polyolefin (A) is preferably a polyolefin which is acid-modified with an α,β-unsaturated carboxylic acid and an acid anhydride thereof. As the α,β-unsaturated carboxylic acid and the acid anhydride thereof, for example, maleic acid, itaconic acid, citraconic acid, and acid anhydrides of these can be mentioned. Of these, the acid anhydride is preferred, and maleic anhydride is more preferred. These α,β-unsaturated carboxylic acids and acid anhydrides thereof can be used in combination of one or two or more.

[0016] From the viewpoint of the adhesion of the polyolefin resin base material to the metal base material, the acid value of the modified polyolefin (A) is preferably 2 mgKOH / g or more. More preferably, it is 3 mgKOH / g or more, further preferably 5 mgKOH / g or more, and particularly preferably 7 mgKOH / g or more. By setting the acid value to be the above lower limit value or more, the adhesion at the polyolefin / metal interface is improved, and the metal adhesion at 25°C and 90°C environments is good. The upper limit of the acid value is preferably 50 mgKOH / g or less. More preferably, it is 45 mgKOH / g or less, further preferably 40 mgKOH / g or less, and particularly preferably 35 mgKOH / g or less. By setting it to be the above upper limit value or less, the adhesion strength is improved because the molecular weight increases and the cohesion is enhanced. Further, the manufacturing efficiency is also improved.

[0017] The acid value of the modified polyolefin (A) can be adjusted by the amounts of the α,β-unsaturated carboxylic acid, the acid anhydride thereof, and the free radical initiator used.

[0018] The weight average molecular weight (Mw) of the modified polyolefin (A) is preferably in the range of 70,000 or more and less than 200,000. More preferably, it is in the range of 75,000 to 150,000, further preferably in the range of 80,000 to 130,000, and most preferably in the range of 85,000 to 10,5000. By setting it to be the above lower limit value or more, the cohesion is good, and excellent adhesion can be exhibited. Further, by setting it to be the above upper limit value or less, the solubility stability and the flowability are excellent, and the handling is good.

[0019] The melting point (Tm) of the modified polyolefin (A) is preferably in the range of 50°C to 130°C, more preferably in the range of 60°C to 125°C. Further preferably, it is in the range of 70°C to 120°C, and most preferably in the range of 85°C to 110°C. By setting it to be the above lower limit value or more, the resin does not melt even in a high temperature environment, the cohesion derived from crystallization is good, and excellent adhesion and heat resistance can be exhibited. Further, by setting it to be the above upper limit value or less, the solubility stability and the flowability are excellent, and the handling at the time of adhesion is good.

[0020] The heat of fusion (ΔH) of the modified polyolefin (A) is preferably in the range of 5 J / g to 60 J / g. More preferably, it is in the range of 10 J / g to 50 J / g, and further preferably, it is in the range of 20 J / g to 40 J / g. By being equal to or more than the above lower limit, the cohesion derived from crystallization is good, and excellent adhesiveness can be exhibited. In addition, by being equal to or less than the above upper limit, the solubility and flowability are excellent, and the workability at the time of adhesion is good.

[0021] As the method for producing the modified polyolefin (A), there is no particular limitation, and for example, a radical grafting reaction (i.e., a reaction in which a radical species is generated with respect to a polymer serving as a main chain, and then an unsaturated carboxylic acid and an acid anhydride are graft-polymerized using the radical species as a polymerization initiation point) or the like can be cited.

[0022] As the radical initiator, there is no particular limitation, and for example, organic peroxides, azonitriles, and the like can be cited, and an organic peroxide is preferably used. As the organic peroxide, there is no particular limitation, and for example, di-t-butyl perphthalate, t-butyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, t-butyl peroxybenzoate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxy-t-amyl acetate, methyl ethyl ketone peroxide, di-t-butyl peroxide, dilauroyl peroxide, and the like can be cited, and as the azonitriles, azobis isobutyronitrile, azobis isopropyl nitrile, and the like can be cited.

[0023] As the modified polyolefin (A), a commercially available product can be used, and for example, the "MODIC" series manufactured by Mitsubishi Chemical Corporation, the "ADMER" series, the "UNISTOLE" series manufactured by Mitsui Chemicals, Inc., the "HARDLEN" series manufactured by Toyobo Co., Ltd., the "UMEX" series manufactured by Sojitz Chemical Corporation, the "AUROREN" series manufactured by Japan Paper Co., Ltd., and the like can be cited.

[0024] The olefin-α-olefin copolymer (B) used in the present application refers to an unmodified random copolymer in which an α-olefin is used as a comonomer. As the comonomer, one or a plurality of kinds of ethylene, propylene, 1-butene, 1-heptene, 1-octene, 4-methyl-1-pentene, vinyl acetate, and the like can be used. Among them, 1-butene is preferable. In addition, as the main body of the olefin-α-olefin copolymer (B), polyethylene, polypropylene, and the like can be used. Among them, polypropylene is preferable. The main body of the olefin-α-olefin copolymer (B) refers to a component that accounts for 50 mol% or more in the total composition of the copolymer. The olefin-α-olefin copolymer (B) used in the present application is particularly preferably a propylene / α-olefin copolymer.

[0025] ​The propylene / α-olefin copolymer is a copolymer of propylene as a main component and an α-olefin. As the α-olefin, one or a plurality of kinds of ethylene, 1-butene, 1-heptene, 1-octene, 4-methyl-1-pentene, vinyl acetate, or the like can be used. The molar ratio of the propylene component to the α-olefin component in the propylene / α-olefin copolymer is not particularly limited, and the propylene component is preferably 50 mol% or more, and more preferably 70 mol% or more. By having the molar ratio of propylene be 50% or more, excellent adhesiveness to a polyolefin resin substrate, particularly to a polypropylene resin substrate, can be exhibited.

[0026] The weight average molecular weight (Mw) of the olefin-α-olefin copolymer (B) is 200,000 or more, and preferably in the range of 200,000 to 1,300,000. More preferably, it is in the range of 300,000 to 1,200,000, further preferably in the range of 400,000 to 1,100,000, and most preferably in the range of 500,000 to 1,000,000. By being equal to or more than the lower limit value described above, the cohesion derived from crystallization is good, and excellent adhesiveness can be exhibited. Furthermore, by being equal to or less than the upper limit value described above, the solubility in an organic solvent is improved, and the dissolution stability is good.

[0027] The melting point (Tm) of the olefin-α-olefin copolymer (B) is in the range of 80°C to 100°C, and preferably in the range of 80°C to 90°C. By being equal to or more than the lower limit value described above, the cohesion derived from crystallization is good, and excellent adhesiveness can be exhibited. Furthermore, by being equal to or less than the upper limit value described above, the dissolution stability and flowability are excellent, and the operability at the time of adhesion is good.

[0028] The heat of fusion (ΔH) of the olefin-α-olefin copolymer (B) is preferably in the range of 20 J / g to 70 J / g. More preferably, it is in the range of 25 J / g to 60 J / g, and further preferably in the range of 30 J / g to 50 J / g. By being equal to or more than the lower limit value described above, the cohesion derived from crystallization is good, and excellent adhesiveness can be exhibited. Furthermore, by being equal to or less than the upper limit value described above, the dissolution stability and flowability are excellent, and the operability at the time of adhesion is good.

[0029] <Adhesive composition> The adhesive composition of the present application contains the modified polyolefin (A) and the olefin-α-olefin copolymer (B) described above.

[0030] The adhesive composition of the present application contains the olefin-α-olefin copolymer (B) in a proportion of 15 to 85 parts by mass relative to 100 parts by mass of the modified polyolefin (A). It is preferable to contain the olefin-α-olefin copolymer (B) in a proportion of 20 parts by mass or more relative to 100 parts by mass of the modified polyolefin (A), further preferably 25 parts by mass or more, and particularly preferably 30 parts by mass or more. By setting to the above lower limit value or more, the cohesion due to the high molecular weight component is good, and excellent adhesion can be exhibited. In addition, it is preferable to contain the olefin-α-olefin copolymer (B) in a proportion of 80 parts by mass or less relative to 100 parts by mass of the modified polyolefin (A), further preferably 75 parts by mass or less, and particularly preferably 70 parts by mass or less. By setting to the above upper limit value or less, the effect of improving the adhesion of the olefin / metal interface due to the modified polyolefin (A) can be exerted, and even in a high temperature environment where the resin softens, excellent adhesion can be exhibited. In addition, the solubility stability is also excellent.

[0031] The weight average molecular weight of the modified polyolefin (A) and the olefin-α-olefin copolymer (B) satisfies the relationship of the weight average molecular weight of (A) ≤ the weight average molecular weight of (B). It is preferable that the weight average molecular weight of (A) < the weight average molecular weight of (B). By satisfying the above formula, both the effect of improving the metal adhesion due to the modified component and the effect of improving the adhesion strength due to the cohesion of the high molecular weight component can be exhibited.

[0032] When the weight average molecular weight of the modified polyolefin (A) and the olefin-α-olefin copolymer (B) satisfies the relationship of the weight average molecular weight of (A) < the weight average molecular weight of (B), the difference between the weight average molecular weight of (A) and (B) is preferably 10,000 or more, more preferably 100,000 or more, further preferably 200,000 or more, and most preferably 300,000 or more. In addition, it is preferably 500,000 or less, more preferably 480,000 or less, and further preferably 450,000 or less.

[0033] The sum of the weight average molecular weight of the modified polyolefin (A) and the olefin-α-olefin copolymer (B) is preferably 450,000 or more, more preferably 500,000 or more, and further preferably 550,000 or more. In addition, it is preferably 700,000 or less, more preferably 650,000 or less, and further preferably 620,000 or less.

[0034] Within the range that does not impair the properties of the present application, the adhesive composition of the present application can be used by mixing various tackifiers, plasticizers, flame retardants, pigments, blocking preventives, and the like additives in addition to the above-mentioned modified polyolefin (A) and the olefin-α-olefin copolymer (B).

[0035] The adhesive composition of the present application can form an adhesive layer exhibiting high adhesive force even without mixing a curing agent. Therefore, the adhesive composition of the present application is preferably substantially free of a curing agent.

[0036] In the adhesive composition of the present application, the content of the curing agent is preferably less than 1 part by mass, more preferably less than 0.5 parts by mass, further preferably less than 0.1 parts by mass, and most preferably the adhesive composition is free of the curing agent, relative to 100 parts by mass of the solid component of the adhesive composition. When the content of the curing agent is large, not only the economy is poor, but also there are concerns that the curing agent self-condenses to cause a decrease in the followability to a substrate and a decrease in the stability of long-term storage.

[0037] Here, the curing agent refers to a known curing agent that forms a crosslinked structure by reacting with the modified polyolefin resin, and examples thereof include isocyanate compounds, epoxy compounds, carbodiimide compounds, oxazoline compounds, and the like.

[0038] The adhesive composition of the present application can further contain an organic solvent (C) without impairing the properties of the present application. As the organic solvent, there is no particular limitation as long as the modified polyolefin (A) and the olefin-α-olefin copolymer (B) can be dissolved or dispersed, and examples thereof include low-polarity solvents such as aliphatic hydrocarbons and alicyclic hydrocarbons, alcohol-based solvents, ether-based solvents, ketone-based solvents, ester-based solvents, and high-polarity solvents. From the viewpoint of storage stability, it is preferable to use a low-polarity solvent and a high-polarity solvent in combination. The content ratio of the high-polarity solvent and the low-polarity solvent is preferably 50 to 3 / 50 to 97 (mass ratio), more preferably 45 to 5 / 55 to 95, and further preferably 40 to 10 / 60 to 90.

[0039] As the aliphatic hydrocarbons, there can be mentioned hexane, heptane, octane, decane, and the like. As the alicyclic hydrocarbons, there can be mentioned cyclohexane, cyclohexene, methylcyclohexane, ethylcyclohexane, and the like. As the alcohol-based solvents, there can be mentioned methanol, ethanol, isopropanol, butanol, pentanol, hexanol, propylene glycol, and the like. As the ether-based solvents, there can be mentioned ethylene glycol mono-n-butyl ether, ethylene glycol mono-i-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-i-butyl ether, triethylene glycol mono-n-butyl ether, tetraethylene glycol mono-n-butyl ether, and the like. As the ketone-based solvents, there can be mentioned acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclohexanone, isophorone, phenylacetone, and the like. As the ester-based solvents, there can be mentioned methyl acetate, ethyl acetate, butyl acetate, methyl propionate, butyl formate, and the like.

[0040] Among the above-mentioned organic solvents, as a low polarity solvent, methylcyclohexane and the like as alicyclic hydrocarbons are preferred; as a high polarity solvent, methyl ethyl ketone and the like as a ketone-based solvent are preferred, with a mixture of methylcyclohexane and methyl ethyl ketone being more preferred. These organic solvents (C) are preferably contained in a range of 80 to 2000 parts by mass, relative to 100 parts by mass of the total amount of the (A) component and the (B) component. More preferably, it is in a range of 90 to 1600 parts by mass, further preferably in a range of 100 to 1200 parts by mass, and particularly preferably in a range of 110 to 900 parts by mass. In the above-mentioned range, the solution state easily becomes good.

[0041] <laminate> The laminate of the present application has a polyolefin resin substrate and the above-mentioned adhesive composition of the present application, and a metal substrate, which are sequentially laminated.

[0042] As a lamination method, a publicly known injection molding technique can be used. For example, an adhesive composition can be applied on the surface of a metal substrate using a suitable coating means such as a roll coater, a bar coater, and the like, and after drying, a polyolefin resin is injection molded on the adhesive composition layer (adhesive layer) formed on the surface of the metal substrate, to obtain a laminate. The thickness of the adhesive layer formed by the above-mentioned adhesive composition is not particularly limited, and is preferably in a range of 0.5 to 30 μm, more preferably in a range of 1.0 to 25 μm, and further preferably in a range of 1.0 to 20 μm.

[0043] As a publicly known injection molding technique, for example, there is a method in which a polyolefin resin is molded by injecting it into a mold in which a metal substrate is installed. More specifically, in the case of using a screw type hot melt molding processing applicator, a polyolefin resin is heated and melted at around 160 to 280°C, and then injected into a mold through an injection nozzle, and after a certain cooling time, the laminate is taken out of the mold, to obtain a laminate.

[0044] The type of the hot melt molding processing applicator is not particularly limited, and for example, ST2 manufactured by Nordson Co., Ltd., vertical type extrusion molding machine IMC-18F9 manufactured by Miki Tekko K.K., and the like can be mentioned.

[0045] <polyolefin resin substrate> As the polyolefin resin substrate, a publicly known polyolefin resin can be appropriately selected. For example, polyethylene, polypropylene, ethylene-propylene copolymer, and the like can be used. Among them, polypropylene is preferably used. The thickness thereof is not particularly limited, and is preferably in a range of 100 to 500 μm, more preferably in a range of 150 to 400 μm, and further preferably in a range of 200 to 300 μm. In addition, pigments, various additives, and the like can be mixed into the polyolefin resin substrate as needed.

[0046] <metal substrate> The metal substrate is not particularly limited, and various metals and alloys thereof such as aluminum, copper, steel, chromium, zinc, duralumin, die-cast, and the like can be used. Further, the shape thereof can be any shape such as a metal foil, a rolled steel sheet, a panel, a pipe, a can, a lid, and the like. In general, from the viewpoint of processability and the like, aluminum is preferred. Further, although it varies depending on the purpose of use, in general, a sheet having a thickness of 0.01 to 10 mm, preferably 0.02 to 5 mm is used. Further, surface treatment can be applied to the surface of the metal substrate in advance, or it can be left untreated. In any case, equivalent effects can be exerted. Examples

[0047] Hereinafter, examples are shown in order to more specifically describe the present application, and the present application is not limited by these examples at all. In addition, the measured values described in the examples are measured by the following methods. Further, in the examples and comparative examples, "parts" alone means "mass parts", and "%" means "mass %".

[0048] (1) Measurement of Weight Average Molecular Weight The weight average molecular weight in the present application is a value measured by gel permeation chromatography (hereinafter, GPC; standard material: polystyrene resin; mobile phase: tetrahydrofuran; chromatographic column: Shodex KF-802 + KF-804L + KF-806L; column temperature: 30°C; flow rate: 1.0 ml / minute; detector: RI detector) manufactured by Shimadzu Corporation.

[0049] (2) Measurement of Melting Point (Tm), Heat of Fusion (ΔH) The melting point and the heat of fusion in the present application are values measured using a differential scanning calorimeter (hereinafter, DSC; Q-2000 manufactured by TA Instrument Japan) by raising the temperature from -50°C to 200°C at a rate of 20°C / minute, then cooling from 200°C to -50°C at a rate of 20°C / minute, and again raising the temperature from -50°C to 200°C at a rate of 20°C / minute, based on the peak top temperature and the area of the melting peak at the time of melting.

[0050] (3) Measurement of Acid Value (Unit: mgKOH / g) The acid value in the present application is the amount of KOH required to neutralize 1 g of a sample, measured according to the test method of JIS K0070 (1992). Specifically, 1 g of the modified polyolefin is dissolved in 100 g of xylene adjusted to 100°C, and titrated with 0.1 mol / L potassium hydroxide ethanol solution [trade name "0.1 mol / L Potassium Hydroxide Ethanol Solution", manufactured by Wako Pure Chemical Industries, Ltd.] at the same temperature using phenothalin as an indicator. At this time, the amount of potassium hydroxide required for titration is converted to mg, and the acid value (mg KOH / g) is calculated.

[0051] (4) Solubility stability The adhesive composition produced in the examples was dissolved in methylcyclohexane / methyl ethyl ketone = 9 / 1 (weight ratio) to a resin solution having a solid content of 20% by mass, and stored at 25°C for 2 weeks (14 days), and the presence or absence of turbidity was confirmed by visual observation, and judged according to the following criteria. O: No turbidity was generated in the resin solution. X: Turbidity was generated in the resin solution.

[0052] (5) Adhesive strength <Manufacture of a laminate for test pieces> An aluminum plate (thickness 100 μm) / adhesive composition layer (thickness 20 μm) / polyolefin resin substrate (thickness 300 μm) / adhesive composition layer (thickness 20 μm) / aluminum plate (thickness 100 μm) 5-layer laminate was produced according to the following method. First, the adhesive composition was dissolved in methylcyclohexane / methyl ethyl ketone = 9 / 1 (weight ratio) to a solid content concentration of 20%, to obtain an adhesive composition solution. Next, the adhesive composition solution was applied to an aluminum plate at room temperature using an applicator, so that the dried adhesive composition had a coating thickness of 20 μm, and the solvent was volatilized using a hot air drier at 120°C for 2 minutes. Thereafter, the aluminum plate was fixed inside an adhesive test mold in such a manner that the adhesive composition layer of the aluminum plate was brought into contact with the molten polyolefin resin, and the polyolefin resin substrate was formed in a manner of 25 mm x 10 mm x thickness 300 μm. As the polyolefin, polypropylene (manufactured by Prime Polymer Co., Ltd., Prime Polypro J107G, MFR: 30 g / 10 minutes) was used. Next, a vertical injection molding machine (THX5S manufactured by Nikkan Industry Co., Ltd.) was used to inject the molten polyolefin resin, and molding was performed. The molding conditions were a molding resin temperature of 240°C, a molding pressure of 50 MPa, a cooling time of 20 seconds, and an injection speed of 30 mm / second. The molded product was removed from the mold, and a 5-layer laminate of an adhesive strength test piece (aluminum plate / adhesive composition layer / polyolefin resin substrate / adhesive composition layer / aluminum plate) in which the aluminum plate to which the adhesive composition was applied was sandwiched with the molded polyolefin resin substrate was obtained.

[0053] <Adhesive strength> The adhesive strength between the aluminum plate and the aluminum plate of the 5-layer laminate was measured with a tensile testing machine. The atmosphere temperature at the time of measurement was set to 25°C or 90°C, the peeling speed was set to 300 mm / min, and the tensile strength at the time of peeling with the T-peeling method was taken as the adhesive strength, the unit of which was N / 25 mm. The adhesion between the polyolefin resin base material and the metal base material was evaluated by the adhesive strength at 25°C; the heat resistance was evaluated by the adhesive strength at 90°C, and the following criteria were used for the determination. ◎: 30 N / 25 mm or more O: 15 N / 25 mm or more and less than 30 N / 25 mm X: less than 15 N / 25 mm

[0054] Production Example of Modified Polyolefin (A) <Production Example 1, Modified Polyolefin (A) PO-1> To a 1 L autoclave, 100 parts by mass of a propylene / 1-butene copolymer ("TAFMER (registered trademark) XM7090" manufactured by Mitsui Chemicals, Inc.), 150 parts by mass of toluene, and 3 parts by mass of maleic anhydride, 1 part by mass of di-t-butyl peroxide were added, and after being warmed to 140°C, further stirred for 3 hours. Thereafter, the obtained reaction liquid was cooled, and then poured into a container filled with a large amount of methyl ethyl ketone, and the resin was precipitated. Thereafter, the liquid containing the resin was subjected to centrifugal separation, and the acid-modified propylene / 1-butene copolymer to which maleic anhydride was grafted, and (poly)maleic anhydride and low-molecular-weight substances were separated and purified. Thereafter, by drying at 70°C under reduced pressure for 5 hours, a maleic anhydride-modified propylene / 1-butene copolymer (PO-1, acid value 5 mgKOH / g, weight average molecular weight 90,000, Tm 90°C, ΔH 30 J / g) was obtained as an acid-modified polyolefin.

[0055] <Production Example 2, Modified Polyolefin (A) PO-2> Except that the propylene / 1-butene copolymer ("TAFMER (registered trademark) XM7090" manufactured by Mitsui Chemicals, Inc.) used in Production Example 1 was changed to a propylene / 1-butene copolymer ("TAFMER (registered trademark) XM7080" manufactured by Mitsui Chemicals), production was carried out in the same manner as in Production Example 1, and a maleic anhydride-modified propylene / 1-butene copolymer (PO-2, acid value 5 mgKOH / g, weight average molecular weight 90,000, Tm 80°C, ΔH 30 J / g) was obtained as an acid-modified polyolefin.

[0056] <Production Example 3, Modified Polyolefin (A) PO-3> The maleic anhydride-modified propylene / 1-butene copolymer (PO-3, acid value 20 mgKOH / g, weight average molecular weight 110,000, Tm 70°C, ΔH 25 J / g) as the acid-modified polyolefin was obtained by the same procedure as in Production Example 1 except that the propylene / 1-butene copolymer ("TAFMER (registered trademark) XM7090" manufactured by Mitsui Chemicals, Inc.) used in Production Example 1 was changed to a propylene / 1-butene copolymer ("TAFMER (registered trademark) XM7070" manufactured by Mitsui Chemicals), the amount of maleic anhydride charged was changed to 16 parts by mass, and the amount of di-t-butyl peroxide charged was changed to 0.5 parts by mass.

[0057] <Production Example 4, Modified Polyolefin (A) PO-4> The maleic anhydride-modified propylene / 1-butene copolymer (PO-4, acid value 19 mgKOH / g, weight average molecular weight 75,000, Tm 90°C, ΔH 25 J / g) as the acid-modified polyolefin was obtained by the same procedure as in Production Example 1 except that the amount of maleic anhydride charged was changed to 13 parts by mass, and the amount of di-t-butyl peroxide charged was changed to 3 parts by mass.

[0058] <Example 1> A binder composition of Example 1 was obtained by mixing 100 parts by mass of PO-1 as the (A) component, 50 parts by mass of S-1 as the (B) component, 450 parts by mass of methylcyclohexane, and 50 parts by mass of methyl ethyl ketone (solid component concentration 20% by mass). The details and evaluation results of the binder composition of Example 1 are shown in Table 1.

[0059] <Examples 2 to 7, Comparative Examples 1 to 4> Binder compositions of Examples 2 to 7 and Comparative Examples 1 to 4 were obtained by changing the mixing amounts of the (A) and (B) components as shown in Table 1, and in the same manner as in Example 1. The details and evaluation results of these binder compositions are shown in Table 1. In addition, the organic solvent (methylcyclohexane / methyl ethyl ketone = 90 / 10 (mass ratio)) was adjusted to a solid component concentration of 20% by mass.

[0060] [Table 1]

[0061] The olefin-α-olefin copolymer (B) used in Table 1 is as follows. S-1: "TAFMER (registered trademark) XM7080" manufactured by Mitsui Chemicals, Inc., propylene / 1-butene copolymer, weight average molecular weight 520,000, melting point 80°C, ΔH 40 J / g S-2: "TAFMER (registered trademark) XM7090" manufactured by Mitsui Chemicals, Inc., propylene / 1-butene copolymer, weight average molecular weight 520,000, melting point 90°C, ΔH 45 J / g

[0062] The other olefin-α-olefin copolymers used in Table 1 are as follows. S-3: "TAFMER (registered trademark) XM7070" manufactured by Mitsui Chemicals, Inc., propylene / 1-butene copolymer, weight average molecular weight 520,000, melting point 70°C, ΔH 35 J / g S-4: "Licocene (registered trademark) PP1602" manufactured by Clariant, ethylene-propylene copolymer, weight average molecular weight 50,000, melting point 65°C, ΔH 15 J / g

[0063] As is clear from Table 1, the adhesion strength at 25°C and 90°C and the dissolution stability at 25°C are all good in Examples 1 to 7. In contrast, in Comparative Example 1, the mixing amount of the olefin-α-olefin copolymer (B) is small, and the cohesion is weak, so the adhesion strength at 90°C decreases and the heat resistance is poor. In Comparative Example 2, the mixing amount of the olefin-α-olefin copolymer (B) is large, so the adhesion at the polypropylene (polyolefin resin base material) / aluminum (metal base material) interface decreases. Although high adhesion strength due to high cohesion is exhibited at 25°C, at 90°C the resin softens and the contribution of cohesion decreases, so the adhesion strength at 90°C decreases and the heat resistance becomes poor. Furthermore, since the olefin-α-olefin copolymer (B) undergoes cohesion, the dissolution stability also deteriorates. In Comparative Example 3, the melting point of the olefin-α-olefin copolymer (B) is low, so the adhesion strength at 90°C decreases and the heat resistance becomes poor. In Comparative Example 4, the weight average molecular weight of the modified polyolefin (A) is higher than that of the olefin-α-olefin copolymer (B), and furthermore the weight average molecular weight and the melting point of the olefin-α-olefin copolymer (B) are low, so the adhesion strength at 90°C decreases and the heat resistance becomes poor. Industrial applicability

[0064] The adhesive composition of the present application has good adhesion and heat resistance of a polyolefin resin base material to a metal base material. In addition, under high-temperature short-time processing conditions such as injection molding, it can exhibit good adhesion strength. Therefore, the laminate of a polyolefin resin base material and a metal base material formed from the adhesive composition of the present application can be widely used in the fields of home appliance outer plates, furniture materials, architectural interior parts, electrical and electronic parts, and the like.

Claims

1. An adhesive composition characterized in that, contains a modified polyolefin (A) and an olefin-α-olefin copolymer (B), and satisfies all of the following (1) to (4): (1) contains the olefin-α-olefin copolymer (B) at a ratio of 15 to 85 parts by mass with respect to 100 parts by mass of the modified polyolefin (A); (2) the weight average molecular weight of the olefin-α-olefin copolymer (B) is 200,000 or more; (3) the melting point of the olefin-α-olefin copolymer (B) is 80°C or higher and 100°C or lower; (4) the weight average molecular weight of the modified polyolefin (A) is ≤ the weight average molecular weight of the olefin-α-olefin copolymer (B).

2. The adhesive composition according to claim 1, wherein the weight average molecular weight of the modified polyolefin (A) is 70,000 or more and less than 200,000.

3. The adhesive composition according to claim 1 or 2, further containing an organic solvent (C).

4. The adhesive composition according to claim 1 or 2, wherein the acid value of the modified polyolefin (A) is 2 to 50 mgKOH / g.

5. The adhesive composition according to claim 1 or 2, which is used for adhesion of a polyolefin resin substrate to a metal substrate.

6. A laminate which has a polyolefin resin substrate, the adhesive composition described in claim 1 or 2, and a metal substrate laminated in this order.

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