Polyolefin-based adhesive composition and laminate

Abstract

[Problem] To provide an adhesive composition which achieves good adhesion between a polyolefin resin base material and a material of a different kind, while exhibiting chipping resistance, and which enables bonding at low temperatures. [Solution] An adhesive composition which contains (A) an acid-modified polyolefin, (B) a stress relaxation agent, and (C) a tackifying agent.

Description

[Technical Field]

[0001] The present invention relates to an adhesive composition and a laminate. [Background technology]

[0002] Polyolefin resins such as polypropylene and polyethylene are inexpensive and have many excellent properties such as moldability, chemical resistance, water resistance, and electrical properties, and therefore have been widely used in recent years as sheets, films, molded products, and the like. However, unlike polar substrates such as polyurethane resins, polyamide resins, acrylic resins, and polyester resins, substrates made of these polyolefin resins (hereinafter referred to as polyolefin substrates) are non-polar and crystalline, and therefore have the disadvantage of being difficult to paint or adhere. Recently, with the trend toward lighter automobiles, the use of olefin-based resin parts in automobile exteriors, including bumpers, has been increasing. Furthermore, efforts to reduce VOCs and CO2 emissions have led to the study of replacing paint with paint-alternative films. Furthermore, adhesive layers with similar adhesive strength are required for both steel sheet and olefin resin parts, and performance such as chipping resistance is also required. Chip resistance refers to the durability of the paint film, preventing it from being locally damaged or peeled off when hit by stones or other objects kicked up while the automobile is moving. Adhesive compositions proposed to date for polyolefin resins include adhesive compositions that exhibit adhesion between polypropylene resin and polyethylene resin, adhesive compositions that exhibit adhesion between olefin-based resins (Patent Documents 1 to 3), and adhesive compositions that exhibit adhesion even when bonding olefin-based resins with resins other than olefin-based resins (Patent Documents 4 to 6).

[0003] [Patent Document 1] Patent application 2017-564927 [Patent Document 2] Patent application 2014-232540 [Patent Document 3] Patent application 2009-548844 [Patent Document 4] Patent Publication No. 2004-292716 [Patent Document 5] Patent Publication No. 2014-234400 [Patent Document 6] Patent Publication No. 2016-89060 Summary of the Invention [Problem to be solved by the invention]

[0004] However, while the adhesive compositions proposed above all exhibit good adhesion between polyolefin resin substrates and metal (aluminum) or between polyolefin resin substrates and polyester (PET) substrates, their adhesion between substrates other than aluminum and PET and polyolefin resin substrates is unknown. Furthermore, all of these are hot-melt adhesives, and require bonding at a high temperature of 180°C. Furthermore, many of the proposed adhesive compositions have not been examined in terms of performance other than adhesion, and no mention is made of multi-adhesion or chipping resistance. The present invention provides an adhesive composition that exhibits good adhesion and chipping resistance between polyolefin resin substrates and polar plastic substrates other than polyolefin resin substrates or metal substrates, and that allows bonding at low temperatures. [Means for solving the problem]

[0005] In order to achieve the above object, the present inventors have conducted extensive research and found that a combination of a specific modified polyolefin, a stress relaxation agent, and a tackifier is effective, leading to the proposal of the following invention. (1) An adhesive composition comprising an acid-modified polyolefin (A), a stress relaxation agent (B), and a tackifier (C), wherein the stress relaxation agent (B) is at least one resin selected from the group consisting of an olefin resin containing a diene monomer as a constituent unit, a vinyl chloride resin, a urethane resin, and an amide resin, and a styrene resin. (2) The adhesive composition according to (1) above, wherein the stress relaxation agent (B) is an olefin resin (B1) and a hydrogenated styrene resin (B2). (3) The adhesive composition according to any one of (1) to (2) above, further comprising a solvent (D). (4) The adhesive composition according to any one of (1) to (3) above, wherein the solvent (D) comprises an alicyclic hydrocarbon solvent (D1) and an ester-based solvent or a ketone-based solvent (D2). (5) The adhesive composition according to any one of (1) to (4) above, wherein the mass ratio of the alicyclic hydrocarbon solvent (D1) to the ester-based solvent or ketone-based solvent (D2) is (D1) / (D2)=95 / 5 to 50 / 50. (6) The adhesive composition according to any one of (1) to (5) above, which contains a curing agent (E). (7) The adhesive composition according to any one of the above (1) to (6), which is used for bonding a polyolefin resin substrate 1 to a substrate 2 different from the substrate 1. (8) A laminate of a polyolefin resin substrate 1 bonded with the adhesive composition according to any one of (1) to (7) above and a substrate 2 different from the substrate 1. [Effects of the Invention]

[0006] The adhesive composition of the present invention contains an acid-modified polyolefin, a stress relaxation agent, and a tackifier, and exhibits excellent adhesion to poorly adhesive substrates such as polyolefins. Furthermore, the composition can be applied by dry lamination, reducing equipment costs and enabling thinner film thicknesses. Furthermore, the composition exhibits excellent adhesion even when heated and bonded at low temperatures (below 90°C), where the thermal shrinkage of polyolefin substrates is minimal.

[0007] The adhesive composition of the present invention not only exhibits adhesion to poorly adhesive substrates such as polyolefins, but also high chipping resistance, making it useful as an adhesive for films to replace exterior automotive paint. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described in detail.

[0009] <Acid-modified polyolefin (A)> The acid-modified polyolefin (A) used in the present invention is not limited, but is preferably one obtained by grafting at least one of an α,β-unsaturated carboxylic acid and an acid anhydride thereof onto a polyolefin.

[0010] As polyolefins, propylene-based resins containing propylene as a constituent component are preferred, with homopolypropylene being particularly preferred, but propylene-α-olefin copolymers can also be used. Propylene-α-olefin copolymers are produced by copolymerizing propylene as the main component with an α-olefin. As α-olefins, for example, one or more of ethylene, 1-butene, 1-heptene, 1-octene, 4-methyl-1-pentene, vinyl acetate, etc. can be used. Of these α-olefins, ethylene and 1-butene are preferred, with 1-butene being particularly preferred.

[0011] The acid-modified polyolefin (A) preferably contains propylene as an olefin component in an amount of 60 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and even more preferably 90 mol% or more. The higher the propylene content, the better the adhesion to polypropylene substrates.

[0012] The molar ratio of propylene to 1-butene in the acid-modified polyolefin (A) is preferably propylene / 1-butene=99 to 60 / 1 to 40, more preferably 98 to 65 / 2 to 35, and even more preferably 90 to 70 / 10 to 30. When the molar ratio of propylene is 60% or more, excellent adhesion to polyolefin substrates can be achieved.

[0013] Examples of at least one of α,β-unsaturated carboxylic acids and their acid anhydrides include maleic acid, itaconic acid, citraconic acid, and their acid anhydrides. Among these, acid anhydrides are preferred, and maleic anhydride is more preferred. Specific examples of the acid-modified polyolefin (A) include maleic anhydride-modified homopolypropylene, maleic anhydride-modified propylene-ethylene copolymer, maleic anhydride-modified propylene-1-butene copolymer, and maleic anhydride-modified propylene-ethylene-1-butene copolymer, and these acid-modified polyolefins can be used alone or in combination of two or more. Of these, maleic anhydride-modified homopolypropylene is preferred.

[0014] The acid value of the acid-modified polyolefin (A) is preferably in the range of 2 to 50 mgKOH / g, more preferably 3 to 40 mgKOH / g, even more preferably 5 to 30 mgKOH / g, and particularly preferably 10 to 20 mgKOH / g. When the acid value is 2 mgKOH / g or more, the molecular weight is high and the adhesive layer exhibits good extensibility. On the other hand, when the acid value is 50 mgKOH / g or more, the adhesive layer exhibits high molecular weight and good extensibility. At OH / g or less, the molecular weight is low and the solution stability at low temperatures tends to be good.

[0015] The crystallinity of the acid-modified polyolefin (A) is preferably in the range of 12 to 70%, more preferably in the range of 15 to 60%, and most preferably in the range of 18 to 50%. When the crystallinity is 12% or more, the cohesive force derived from the crystals is strong, resulting in excellent adhesion to the substrate. On the other hand, when the crystallinity is 70% or less, the cohesive force derived from the crystals is moderate, resulting in good adhesion.

[0016] The heat of fusion of the modified polyolefin (A) is preferably in the range of 25 to 80 J / g, more preferably in the range of 28 to 75 J / g, and most preferably in the range of 30 to 70 J / g. When it is 25 J / g or more, the cohesive force derived from the crystals is strong, and the adhesiveness is excellent. On the other hand, when it is 80 J / g or less, the cohesive force derived from the crystals is moderate, and the adhesiveness is good.

[0017] The acid-modified polyolefin (A) may be chlorinated.

[0018] The melting point (Tm) of the acid-modified polyolefin (A) is preferably 50°C or higher and 130°C or lower. More preferably, it is 55°C or higher, and even more preferably, it is 60°C or higher. Furthermore, it is more preferably 125°C or lower, even more preferably, it is lower than 120°C, and even more preferably, it is 115°C or lower, and most preferably, it is 110°C or lower. At 50°C or higher, the cohesive force derived from crystals becomes strong, and adhesiveness is good. On the other hand, at 130°C or lower, solution stability and fluidity are good, and operability during bonding is excellent. Furthermore, bonding is possible even at low temperatures.

[0019] The weight-average molecular weight (Mw) of the acid-modified polyolefin (A) is preferably in the range of 10,000 to 200,000, more preferably in the range of 20,000 to 180,000, even more preferably in the range of 30,000 to 160,000, particularly preferably in the range of 35,000 to 140,000, and most preferably in the range of 40,000 to 120,000. When it is 10,000 or more, the cohesive force is strong and the adhesiveness is good. On the other hand, when it is 200,000 or less, the fluidity is high, the operability during adhesion is good, and the solution stability at low temperatures is good.

[0020] The method for producing the acid-modified polyolefin (A) is not particularly limited, and examples thereof include a radical graft reaction (i.e., a reaction in which radical species are generated in a polymer that becomes the main chain, and an unsaturated carboxylic acid and an acid anhydride are graft polymerized using the radical species as a polymerization initiation point).

[0021] The radical generator is not particularly limited, but is preferably an organic peroxide.The organic peroxide is not particularly limited, but includes peroxides such as di-tert-butyl peroxyphthalate, tert-butyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxypivalate, methyl ethyl ketone peroxide, di-tert-butyl peroxide, lauroyl peroxide, etc.; azonitriles such as azobisisobutyronitrile, azobisisopropionitrile, etc.

[0022] These acid-modified polyolefins (A) may be used alone or in combination of two or more.

[0023] <Stress relaxation agent (B)> The adhesive composition of the present invention contains a stress relaxation agent (B). By including the stress relaxation agent (B), it is possible to reduce the internal stress after the adhesive film is formed, improve adhesion to the substrate, and improve chipping resistance.

[0024] The content of the stress relaxation agent (B) used in the present invention is preferably 1 part by mass or more and 300 parts by mass or less per 100 parts by mass of the acid-modified polyolefin (A). More preferably, it is 5 parts by mass or more and 200 parts by mass or less, even more preferably 10 parts by mass or more and 100 parts by mass or less, particularly preferably 15 parts by mass or more and 85 parts by mass or less, even more preferably 20 parts by mass or more and 70 parts by mass or less, and most preferably 25 parts by mass or more and 60 parts by mass or less. Furthermore, when it is 1 part by mass or more, compatibility is good, a stress relaxation effect is generated, and chipping resistance is good. On the other hand, when it is 100 parts by mass or less, compatibility is good, adhesion is good, and chipping resistance is good.

[0025] The stress relaxation agent (B) is at least one resin selected from the group consisting of olefin resins, vinyl chloride resins, urethane resins, and amide resins containing a diene monomer as a structural unit, and a styrene resin. Examples of the olefin resins containing a diene monomer as a structural unit, such as ethylene-α-olefin-diene rubber, include vinyl chloride resins such as polyvinyl chloride elastomers, urethane resins such as polyurethane, and amide resins such as polyamide elastomers. Examples of the styrene resins include styrene resins such as styrene-ethylene-butylene-styrene resins and their hydrogenated derivatives, and these may be modified. It is preferable to use one or more resins selected from the group consisting of olefin resins, vinyl chloride resins, urethane resins, and amide resins containing a diene monomer as a structural unit. It is preferable to use two or more types of stress relaxation agent (B), including a styrene resin and an olefin resin containing a diene monomer, and it is particularly preferable to use a hydrogenated styrene resin and an olefin resin. The styrene resin is preferably a hydrogenated styrene resin.

[0026] The olefin resin (B1) is preferably an olefin resin containing a diene monomer as a structural unit and is an amorphous resin. Examples include propylene-butene, ethylene-propylene-butene copolymer, butadiene, and ethylene-α-olefin-diene rubber. The olefin resin may be an acid-modified product.

[0027] The weight-average molecular weight (Mw) of the olefin resin (B1) is preferably 20,000 to 200,000. It is more preferably 25,000 to 160,000, even more preferably 30,000 to 140,000, particularly preferably 35,000 to 120,000, even more preferably 37,000 to 100,000, and most preferably 40,000 to 80,000. When it is 1,000 or more, compatibility with the acid-modified polyolefin (A) is adequate, stress relaxation effects are exhibited, and adhesiveness tends to be good. Furthermore, when it is 200,000 or less, compatibility with the acid-modified polyolefin (A) is significantly improved.

[0028] The hydrogenated styrene resin (B2) is a resin containing styrene in the skeleton, and is not particularly limited, but examples thereof include styrene-ethylene-butylene-styrene resin, styrene-ethylene-propylene-styrene resin, etc. Styrene-ethylene-butylene-styrene resin is particularly preferred.

[0029] The MFR value of the hydrogenated styrene-based resin (B2) is preferably 0.1 g / 10 min to 50 g / 10 min under conditions (ISO 1133) of extrusion at 230°C under a load of 2.16 kgf. More preferably, it is 0.3 g / 10 min to 45 g / 10 min, even more preferably 0.5 g / 10 min to 40 g / 10 min, particularly preferably 1 g / 10 min to 35 g / 10 min, even more preferably 1.2 g / 10 min to 30 g / 10 min, and most preferably 2 g / 10 min to 20 g / 10 min. A MFR of 0.1 g / 10 min or more provides favorable compatibility with the acid-modified polyolefin (A), and tends to facilitate the development of a stress relaxation effect. Furthermore, a MFR of 50 g / 10 min or less significantly improves compatibility with the acid-modified polyolefin (A).

[0030] The stress relaxation agent (B) is preferably acid-modified, and its acid value is preferably 0.01 mgKOH / g or more and 50 mgKOH / g or less. It is more preferably 0.05 mgKOH / g or more and 45 mgKOH / g or less, even more preferably 0.1 mgKOH / g or more and 40 mgKOH / g or less, particularly preferably 0.5 mgKOH / g or more and 35 mgKOH / g or less, even more preferably 1 mgKOH / g or more and 30 mgKOH / g or less, and most preferably 1.5 mgKOH / g or more and 25 mgKOH / g or less. When it is 0.01 mgKOH / g or more and 50 mgKOH / g or less, it has a good compatibility with the acid-modified polyolefin (A) and good adhesiveness.

[0031] In 100 parts by mass of the stress relaxation agent (B), (B1) is preferably 1% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 48% by mass or less, and even more preferably 10% by mass or more and 46% by mass or less. When it is 1% by mass or more and 50% by mass or less, good adhesion is obtained.

[0032] In 100 parts by mass of the stress relaxation agent (B), (B2) is preferably 50% by mass to 99% by mass, more preferably 52% by mass to 95% by mass, and even more preferably 55% by mass to 90% by mass. By being 50% by mass to 99% by mass, both adhesiveness and chipping resistance can be achieved.

[0033] When (B1) and (B2) are used as the stress relaxation agent (B), the mass ratio of (B1) to (B2) is preferably 1 / 99 to 50 / 50, more preferably 5 / 95 to 49 / 51, even more preferably 10 / 90 to 48 / 52, particularly preferably 15 / 85 to 47 / 53, even more preferably 20 / 80 to 46 / 54, and most preferably 25 / 75 to 45 / 55. A ratio within the range of 1 / 99 to 50 / 50 provides good adhesion and chipping resistance.

[0034] When (B1) and (B2) are used as the stress relaxation agent (B), the total amount of (B1) and (B2) is preferably 50 mass% or more, more preferably 60 mass% or more, and most preferably 70 mass% or more, based on 100 mass parts of the stress relaxation agent (B). When the total amount is 50 mass% or more, good adhesion and chipping resistance are achieved. <Tackifier (C)> The adhesive composition of the present invention contains a tackifier (C). By including a tackifier, the adhesive surface can be maintained after the adhesive film is formed, and the adhesion to the substrate can be improved.

[0035] The content of the tackifier (C) used in the present invention is preferably 1 part by mass or more and 500 parts by mass or less per 100 parts by weight of the acid-modified polyolefin (A). More preferably, it is 5 parts by mass or more and 300 parts by mass or less, even more preferably 10 parts by mass or more and 100 parts by mass or less, particularly preferably 15 parts by mass or more and 90 parts by mass or less, even more preferably 20 parts by mass or more and 85 parts by mass or less, and most preferably 30 parts by mass or more and 65 parts by mass or less. Furthermore, when it is 1 part by mass or more, the solution viscosity is moderate and the solution stability is good. On the other hand, when it is 500 parts by mass or less, the surface tackiness is moderate and adhesiveness is exhibited well, and accordingly, chipping resistance is also good.

[0036] The softening point of the tackifier (C) used in the present invention is preferably 60°C or higher. It is more preferably 62°C or higher, even more preferably 65°C or higher, particularly preferably 70°C or higher, even more preferably 75°C or higher, and most preferably 80°C or higher. It is also preferably 150°C or lower, even more preferably 138°C or lower, particularly preferably 135°C or lower, even more preferably 130°C or lower, and most preferably 128°C or lower. When the softening point is 60°C or higher, the tackifier is less likely to bleed out onto the surface at room temperature, resulting in a smooth surface and good adhesiveness. When the softening point is 140°C or lower, tackiness is generated at room temperature and good adhesiveness is achieved. These may be used alone or in combination of two or more.

[0037] The tackifier (C) of the present invention can improve compatibility and storage stability while maintaining good adhesiveness by blending tackifiers with different softening points in an appropriate ratio. For example, in the present application, a tackifier (C1) having a softening point of 110°C to 150°C and a tackifier (C2) having a softening point of 75°C to less than 110°C can be combined. The tackifier (C1) is particularly preferably 115°C to 140°C, most preferably 120°C to 130°C. The tackifier (C2) is particularly preferably 75°C to 100°C, most preferably 80°C to 95°C. Combining the above two types can improve adhesiveness while preventing bleed-out. The mass ratio of (C1) to (C2) (C1) / (C2) is preferably 90 / 10 to 50 / 50, more preferably 85 / 15 to 60 / 40, and even more preferably 78 / 22 to 65 / 35. When the content is within the above range, good compatibility and storage stability are achieved, and good adhesive properties can be exhibited.

[0038] Various types of tackifiers (C) can be used in the present invention, including, for example, petroleum resins (aliphatic, alicyclic, aromatic, etc.), terpene resins (polymers of α-pinene, β-pinene, limonene, etc.), aromatic hydrocarbon-modified terpene resins, rosin-based resins (gum rosin, tall oil rosin, wood rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, maleated rosin, rosin ester, etc.), and terpene phenol resins, with rosin-based resins being particularly preferred. These may be used alone or in combination of two or more.

[0039] The tackifier (C) used in the present invention may be one having a hydroxyl group.

[0040] <Solvent (D)> The adhesive composition of the present invention may contain a solvent (D). The solvent (D) is not particularly limited as long as it can dissolve or disperse the acid-modified polyolefin (A), the stress relaxation agent (B), and the tackifier (C), but is preferably an alicyclic hydrocarbon solvent (D1), an ester-based solvent, or a ketone-based solvent (D2). For example, the alicyclic hydrocarbon solvent (D1) may be cyclohexane, methylcyclohexane, ethylcyclohexane, etc. The ester-based solvent or ketone-based solvent (D2) may be ethyl acetate, propyl acetate, butyl acetate, methyl ethyl ketone, etc. Among these, cyclohexane and butyl acetate are preferred. These may be used alone or in any combination of two or more.

[0041] The solvent (D) used in the present invention can be a mixed solvent containing an alicyclic hydrocarbon solvent (D1) and an ester solvent or a ketone solvent (D2). By using a mixed solvent of an alicyclic hydrocarbon solvent and an ester solvent or a ketone solvent, the solubility of the adhesive composition can be improved.

[0042] When the mixed solvent is used, the mass ratio of the alicyclic hydrocarbon solvent (D1) to the ester solvent or ketone solvent (D2) is preferably (D1) / (D2) = 99 / 1 to 50 / 50. It is more preferably 95 / 5 to 60 / 40, and particularly preferably 90 / 10 to 70 / 30. If the alicyclic hydrocarbon (D1) is more than the above range, the viscosity may be high, causing coating unevenness and reducing adhesion. When the alicyclic hydrocarbon (D1) is contained within the above range, the solubility of the resin is good.

[0043] The solvent (D) can be contained in an amount ranging from 10 to 2000 parts by mass relative to 100 parts by mass of the acid-modified polyolefin (A). The amount is preferably 25 to 1500 parts by mass, more preferably 50 to 1000 parts by mass, even more preferably 100 to 900 parts by mass, and even more preferably 100 to 800 parts by mass. A content within the above range is advantageous in terms of production costs and transportation costs.

[0044] <Hardening agent (E)> The curing agent (E) used in the present invention is not particularly limited, but epoxy compounds, isocyanate compounds, compounds containing an oxazoline group or a carbodiimide group, silane coupling agents, etc. can be used as appropriate, and isocyanate compounds are preferred in terms of good adhesion to resin substrates.

[0045] The isocyanate compound used in the present invention is not particularly limited, and diisocyanates, triisocyanates, and compounds derived therefrom can be preferably used. Examples of the diisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate, bis(4-isocyanatocyclohexyl)methane, and hydrogenated diphenylmethane diisocyanate. Further examples include compounds derived from the diisocyanates, such as isocyanurates, adducts, biurets, uretdiones, and allophanates of the diisocyanates, prepolymers having isocyanate residues (low polymers obtained from diisocyanates and polyols), triglycidyl isocyanurate, and complexes thereof. These may be used alone or in any combination of two or more.

[0046] As the isocyanate compound used in the present invention, those having an isocyanurate of the above diisocyanate compound are preferred because they have excellent adhesion to resin substrates.

[0047] The epoxy compound used in the present invention is not particularly limited, and epoxy resins and compounds derived therefrom are preferably used, more preferably bifunctional epoxies. Specific examples include glycidylamine-type epoxy resins, glycidyl ether-type epoxy resins such as bisphenol A, phenol novolac-type epoxy resins, and cresol novolac-type epoxy resins, glycidyl ester-type epoxy resins such as hexahydrophthalic acid glycidyl ester and dimer acid glycidyl ester, and alicyclic or aliphatic epoxides such as 3,4-epoxycyclohexylmethylcarboxylate, epoxidized polybutadiene, and epoxidized soybean oil. These may be used alone or in combination of two or more.

[0048] The amount of curing agent (E) used in the present invention is preferably 10 parts by mass or less per 100 parts by mass of the total solid content of the adhesive, including the acid-modified polyolefin (A), stress relaxation agent (B), and tackifier (C). A range of 8 parts by mass or less is particularly preferred, more preferably 6 parts by mass or less, even more preferably 4 parts by mass or less, and particularly preferably 3 parts by mass or less. Also, 0.01 parts by mass or more is preferred. A range of 0.05 parts by mass or more is particularly preferred, more preferably 0.1 parts by mass or more, even more preferably 0.3 parts by mass or more, and particularly preferably 0.5 parts by mass or more. Addition of a curing agent results in a sufficient crosslinked structure and improved heat resistance. When the amount is 10 parts by mass or less, the pot life is extended and coating stability is improved. Furthermore, cure shrinkage is reduced, improving adhesion to substrates.

[0049] The adhesive composition of the present invention may contain additives such as various plasticizers, curing accelerators, flame retardants, pigments, and antiblocking agents in addition to the acid-modified polyolefin (A), stress relaxation agent (B), and tackifier (C), as long as the performance of the present invention is not impaired.

[0050] <Adhesive composition> When the adhesive composition of the present invention contains a solvent (D), the ratio of the total amount of the acid-modified polyolefin (A), stress relaxation agent (B), and tackifier (C) to the amount of solvent (D) in the adhesive composition is preferably 5 / 95 to 100 / 0, more preferably 7 / 93 to 40 / 60, even more preferably 10 / 90 to 35 / 65, and particularly preferably 12 / 88 to 30 / 70. Within this range, the storage stability and coatability tend to be good.

[0051] <Laminate> The laminate of the present invention is obtained by laminating a polyolefin resin substrate 1 and a polyolefin substrate 1 or a dissimilar substrate 2 with the adhesive composition of the present invention. The dissimilar substrate 2 is a substrate different from the polyolefin substrate 1. For example, if the polyolefin substrate 1 is polypropylene, the dissimilar substrate 2 is an ABS resin other than polypropylene, polycarbonate, zinc-plated steel sheet, or the like.

[0052] The laminate of the present invention described above is useful for, for example, automobile parts such as bumpers, instrument panels, trims, garnishes, and other vehicle parts, such as interior materials for Shinkansen bullet trains, home appliance parts such as televisions, washing machine tubs, refrigerator parts, air conditioner parts, and vacuum cleaner parts, mobile devices and communication devices such as mobile phone terminals and laptop computers, touch panels for various devices, and everyday items.

[0053] As a lamination method, a conventionally known laminate manufacturing technique can be used. For example, although not particularly limited, an adhesive composition is applied to the surface of a substrate using a suitable application means such as an applicator or a bar coater, and then dried. After drying, while the layer of the adhesive composition (adhesive layer) formed on the surface of the substrate is in a molten state, another substrate can be laminated and bonded (laminate or heat-sealed) to the coated surface to obtain a laminate. Whether lamination or heat-sealed is used to prepare a laminate, sufficient adhesion can be ensured. The thickness of the adhesive layer formed from the adhesive composition is not particularly limited, but is preferably 0.5 to 60 μm, more preferably 1 to 50 μm, and even more preferably 2 to 40 μm.

[0054] <Polyolefin resin substrate (film)> The polyolefin resin substrate may be appropriately selected from conventionally known polyolefin resins. For example, polyethylene, polypropylene, ethylene-propylene copolymer, etc. can be used, but are not particularly limited thereto. Among these, the use of a non-oriented polypropylene film (hereinafter also referred to as CPP) is preferred. Its thickness is not particularly limited, but is preferably 20 to 100 μm, more preferably 25 to 95 μm, and even more preferably 30 to 90 μm. The polyolefin resin substrate may be blended with pigments or various additives, or may be surface-treated, as necessary.

[0055] <Polyolefin resin substrate (molded body)> The polyolefin resin substrate may be appropriately selected from conventionally known polyolefin resins. For example, polyethylene, polypropylene, ethylene-propylene copolymer, etc. can be used, but are not particularly limited thereto. Among these, polypropylene resin substrates are preferred. The thickness is not particularly limited, but is preferably 0.1 to 100 mm, more preferably 0.5 to 90 mm, and even more preferably 1 to 80 mm. The polyolefin resin substrate may be blended with pigments or various additives as needed, or may be surface-treated.

[0056] <Other heterogeneous substrates (molded bodies)> Examples of materials that can be used for the different substrate include ABS resin, polycarbonate, polyvinyl chloride, acrylic resin, urethane resin, galvanized steel plate, ED steel plate, and Al. There are no particular limitations on the thickness, but it is preferably 0.1 to 100 mm, more preferably 0.5 to 90 mm, and even more preferably 1 to 80 mm. The substrate may be surface-treated or left untreated. Similar effects can be achieved in either case. [Example]

[0057] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0058] <Production Example of Acid-Modified Polyolefin (A)> Manufacturing Example 1 A 1-L autoclave was charged with 100 parts by mass of polypropylene (Tm: 80°C, weight-average molecular weight 135,000), 150 parts by mass of toluene, 8.5 parts by mass of maleic anhydride, and 4 parts by mass of di-tert-butyl peroxide. The mixture was heated to 140°C and then stirred for an additional hour. After completion of the reaction, the reaction solution was poured into a large amount of methyl ethyl ketone to precipitate a resin. This resin was further washed several times with methyl ethyl ketone to remove unreacted maleic anhydride. The resulting resin was dried under reduced pressure to obtain an acid-modified polyolefin, maleic anhydride-modified polypropylene (A-1, acid value 12 mg KOH / g-resin, weight-average molecular weight 60,000, Tm 80°C, heat of fusion 31 J / g).

[0059] Manufacturing Example 2 A maleic anhydride-modified polypropylene (A-2, acid value 12 mg KOH / g-resin, weight-average molecular weight 45,000, Tm 80°C, heat of fusion 34 J / g), an acid-modified polyolefin, was obtained in the same manner as in Production Example 1, except that the polypropylene used in Production Example 1 was changed to another polypropylene (Tm: 80°C, weight-average molecular weight 45,000).

[0060] Manufacturing Example 3 A maleic anhydride-modified propylene-butene copolymer (A-3, acid value 12 mg KOH / g-resin, weight average molecular weight 90,000, Tm 80°C, heat of fusion 48 J / g), an acid-modified polyolefin, was obtained in the same manner as in Production Example 1, except that the polypropylene used in Production Example 1 was changed to a propylene-butene copolymer (Tm: 83°C, propylene 80 mol%, butene 20 mol%).

[0061] Production Example 4 A maleic anhydride-modified propylene-butene copolymer (A-4, acid value 25 mg KOH / g-resin, weight average molecular weight 60,000, Tm 95°C, heat of fusion 61 J / g), which is an acid-modified polyolefin, was obtained by the same procedure as in Production Example 1, except that the polypropylene used in Production Example 1 was changed to a propylene-butene copolymer (Tm: 98°C, propylene 85 mol%, butene 15 mol%) and the amount of maleic anhydride was changed to 20 parts by mass.

[0062] Example 1 In a 500 ml four-neck flask equipped with a water-cooled reflux condenser and a stirrer, 100 parts by mass of the maleic anhydride-modified polypropylene (A-1) obtained in Production Example 1, 20 parts by mass of stress relaxation agent (B1-1), 25 parts by mass of stress relaxation agent (B2-1), 35 parts by mass of tackifier (C-1), 15 parts by mass of (C-2), curing agent (E-1), 432 parts by mass of cyclohexane (D1), and 48 parts by mass of butyl acetate (D2) were charged, and the mixture was heated to 70 ° C. with stirring, and after continuing stirring for 1 hour, cooled to obtain adhesive composition 1. Using this adhesive composition 1, a laminate was produced by the following method.

[0063] Fabrication of laminates between polyolefin resin substrates or other different substrates (heat seal bonding) An unstretched polypropylene film (Pylen (registered trademark) Film CT, manufactured by Toyobo Co., Ltd., thickness 80 μm) (hereinafter also referred to as CPP) was used as the polyolefin resin substrate. The obtained adhesive composition was applied to the polyolefin resin substrate using an applicator, adjusting the thickness of the adhesive layer after drying to about 20 μm. The applied surface was dried in a hot air dryer in an atmosphere of 100°C for 3 minutes, yielding a polyolefin resin substrate laminated with an adhesive layer about 20 μm thick. A polypropylene (PP) test plate (Nippon Test Panel, 2 mm thick), an ABS test plate (Nippon Test Panel, 2 mm thick), a polycarbonate (PC) test plate (Nippon Test Panel, 2 mm thick), or a galvanized steel plate (Asahi B-Techno, 0.8 mm thick) was placed on the surface of the adhesive layer, and the plates were bonded using a Tester Sangyo heat seal tester (TP-701-B) at a heat seal temperature of 90°C (55°C on the test plate side) under 0.3 MPa for 15 seconds, and then aged at room temperature for 1 day to obtain a laminate. The adhesive properties of the resulting laminate were evaluated. The results are shown in Table 1.

[0064] (Examples 2 to 19, Comparative Examples 1 to 6) Adhesive compositions 2 to 25 were prepared in the same manner as in Example 1, except that the acid-modified polyolefin (A), stress relaxation agent (B), tackifier (C), and curing agent (E) were changed as shown in Table 1. Laminates were prepared using the resulting adhesive compositions 2 to 25 in the same manner as in Example 1, and adhesion evaluations were carried out. The evaluation results are shown in Table 1.

[0065] [Table 1]

[0066] The stress relaxation agents (B) used in Table 1 are as follows: B1-1 and B1-2 are olefin resins containing diene monomers as structural units, B2-1, B2-2, and B2-3 are hydrogenated styrene resins, and B3 is a non-hydrogenated styrene resin. B1-1: Trilene (registered trademark) 65 (Mw: 47,000) manufactured by Lion Elastomers B1-2: Trilene (registered trademark) 77 (Mw: 27,000) manufactured by Lion Elastomers B2-1: Tuftec (registered trademark) M1911 manufactured by Asahi Kasei Corporation (MFR: 4.5 g / 10 min, acid value: 2.1 mg KOH / g) B2-2: Tuftec (registered trademark) M1913 manufactured by Asahi Kasei Corporation (MFR: 4 g / 10 min, acid value: 10.4 mg KOH / g) B2-3: Tuftec (registered trademark) M1943 manufactured by Asahi Kasei Corporation (MFR: 8 g / 10 min, acid value: 10.4 mg KOH / g) B3-1: Asahi Kasei Corporation, Tufprene (registered trademark) A (MFR: 1.3 g / 10 min)

[0067] The tackifiers (C) used in Table 1 are as follows: C-1: Haritack (registered trademark) FK125 (rosin ester tackifier, softening temperature 125°C) manufactured by Harima Chemicals Co., Ltd. C-2: Haritack (registered trademark) F85 (rosin ester tackifier, softening temperature 85°C) manufactured by Harima Chemicals Co., Ltd. C-3: Pine Crystal (registered trademark) KE-311 (rosin-based tackifier, softening temperature 95°C) manufactured by Arakawa Chemical Industries, Ltd. C-4: Pine Crystal (registered trademark) KE-359 manufactured by Arakawa Chemical Industries, Ltd. (rosin-based tackifier, softening temperature 100°C, hydroxyl value: 37 to 48 mg KOH / g-resin) C-5: YS Polyster (registered trademark) T80 (terpene phenol-based tackifier, softening temperature 80°C) manufactured by Yasuhara Chemical Co., Ltd.

[0068] The curing agent (E) used in Table 1 is as follows. E-1: Tosoh Corporation (registered trademark) Coronate HX

[0069] The acid-modified polyolefins, stress relaxation agents, tackifiers, adhesive compositions and laminates obtained as described above were subjected to analytical measurements and evaluations according to the following methods. <Acid value measurement> The acid value (mg KOH / g) in the present invention refers to the amount of KOH required to neutralize 1 g of acid-modified polyolefin (A) and hydrogenated styrene-based resin (B2), and was measured in accordance with the test method of JIS K0070 (1992). Specifically, 1 g of acid-modified polyolefin was dissolved in 100 g of xylene adjusted to 100°C, and then titrated at the same temperature with a 0.1 mol / L potassium hydroxide ethanol solution (trade name "0.1 mol / L ethanolic potassium hydroxide solution", manufactured by Wako Pure Chemical Industries, Ltd.) using phenolphthalein as an indicator. The amount of potassium hydroxide required for the titration was converted to mg to calculate the acid value (mg KOH / g).

[0070] <Measurement of weight average molecular weight (Mw)> The number average molecular weight in the present invention was measured using a gel permeation chromatograph Alliance e2695 manufactured by Nihon Waters (hereinafter referred to as GPC, standard substance: polystyrene resin, mobile phase: tetrahydrofuran, column: Shodex KF-806 + KF-803, column temperature: 40°C, flow rate: 1.0 ml / min, detector: photodiode array detector (wavelength 254 nm = ultraviolet light)).

[0071] <Measurement of crystallinity> The adhesive composition was applied to the surface of a Teflon (registered trademark) sheet using an applicator, dried, and then peeled off to obtain a film-like adhesive composition. XRD measurement was then performed under the following conditions. Measurement equipment: Rigaku Denki X-ray diffractometer RINT2500 Target: Cu Tube voltage: 40kV Tube current: 200mA Collimator: 1mmφ Slit: Vertical 2°, Horizontal 1 / 2° Photoreceptor: Ni filter, scintillation counter Scanning range: 2θ / θ The crystallinity was calculated from the obtained XRD diffraction peaks.

[0072] <Melt point and heat of fusion measurement> In the present invention, the melting point and heat of fusion were measured from the top temperature and area of the melting peak when, after holding at -50°C for 5 minutes using a differential scanning calorimeter (hereinafter, DSC, manufactured by TA Instruments Japan, Q-2000), the temperature was raised for melting at a rate of 10°C / min, held at 230°C for 2 minutes when melted at 230°C, cooled to resinify at a rate of 10°C / min to -50°C, and then when the temperature was raised for melting again at a rate of 10°C / min.

[0073] <Method for Measuring MFR> The MFR value in the present invention was measured in accordance with the test method of ISO1133. Specifically, it is the measured value when extruding using MELT INDEXER X416 manufactured by Takara Kogyo Co., Ltd. at 230°C under a load of 2.16 kgf.

[0074] <Evaluation of Adhesiveness> The laminate was cut into strips 15 mm long, and the adhesiveness was evaluated according to the following criteria by a 180° peel test. The 180° peel test conforms to the test method of ASTM-D1876-61, and using a tensilon RTM-100 manufactured by Orientec Corporation, the peel strength at a tensile speed of 50 mm / min was measured in an environment of 25°C. The peel strength (N / 15 mm) between different base materials / polyolefin resin base materials was taken as the average value of two test values.

[0075] <Chipping Resistance Test> It was carried out using a flying stone tester (trade name "JA400", manufactured by Suga Test Instruments Co., Ltd.). The test coating plate was installed on the specimen holder, and at room temperature, 100 g of granite crushed stones of No. 6 particle size were collided with the test plate at an angle of 90 degrees by compressed air of 480 - 520 kPa from a position 30 cm away from the test plate. Then, the obtained test plate was rinsed with water, dried, and an adhesive tape was attached to the coating surface. Then, the above adhesive tape was peeled off, and it was evaluated according to the following criteria from the peeled area where PP, ABS, PC base material, and galvanized steel sheet were exposed. 〇: The ratio of the peeled area to the original area is less than 6%. △: The ratio of the peeled area to the original area is 6% or more and less than 10%. ×: The ratio of the peeled area to the original area is 10% or more.

[0076] <Measurement of breaking elongation of coating film> The elongation of the coating film in the present invention was measured by preparing a cast film with a thickness of 50 μm and measuring it at a tension speed of 50 mm / min in an environment of 25° C. using a Tensilon RTM-100 manufactured by Orientec Corporation. The coating film was cut into a size of 60 × 15 mm, and the elongation was calculated using the following formula. {(length at break of coating film - initial length of coating film) / initial length of coating film} x 100(%) [Industrial Applicability]

[0077] The adhesive composition of the present invention contains an acid-modified polyolefin, a stress relaxation agent, and a tackifier, and exhibits excellent adhesion and chipping resistance not only to non-polar substrates such as polyolefins, but also to polar substrates and other dissimilar substrates such as metals. Furthermore, since the composition can be applied by dry lamination, equipment costs can be reduced and film thickness can be reduced. Furthermore, the composition exhibits excellent adhesion and good elongation even when heated and bonded at low temperatures of 90°C or less, where the thermal shrinkage of polyolefin substrates is minimal. Therefore, the adhesive composition of the present invention can be widely used as an adhesive for a variety of applications, including as a paint replacement film for bonding various types of substrates together.

Claims

1. An adhesive composition comprising an acid-modified polyolefin (A), a stress relaxation agent (B), and a tackifier (C), wherein the stress relaxation agent (B) is an olefin-based resin and a styrene-based resin containing a diene-based monomer as a constituent unit.

2. The adhesive composition according to claim 1 , further comprising a solvent (D).

3. The adhesive composition according to claim 2 , wherein the solvent (D) comprises an alicyclic hydrocarbon solvent (D1) and an ester-based solvent or a ketone-based solvent (D2).

4. 4. The adhesive composition according to claim 3, wherein a mass ratio of the alicyclic hydrocarbon solvent (D1) to the ester solvent or ketone solvent (D2) is (D1) / (D2)=95 / 5 to 50 / 50.

5. The adhesive composition according to any one of claims 1 to 4, further comprising a curing agent (E).

6. The adhesive composition according to any one of claims 1 to 5, which is used to bond a polyolefin resin substrate 1 to a substrate 2 different from said substrate 1.

7. A laminate comprising a polyolefin resin substrate 1 bonded with the adhesive composition according to any one of claims 1 to 6 and a substrate 2 different from said substrate 1.

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