Hot-melt adhesive, adhesive-coated protective sheet, and method for manufacturing the same

Abstract

To provide: an adhesive for forming a protective sheet with an adhesive that can be applied to adherends such as headrest surfaces, backrest surfaces, seat surfaces, kitchen partition members, etc. without heating; a protective sheet with an adhesive; and a protective sheet with an adhesive that can be applied without stringing, does not contaminate the surface to be applied, and can be easily replaced even after it becomes dirty.SOLUTION: Provided is a hot-melt adhesive of which components are a block copolymer (a) with polymer block that contains a polymer block containing a structural unit derived from a methacrylic acid alkyl ester in which the alkyl group has 1 to 3 carbon atoms and a structural unit derived from an acrylic acid alkyl ester in which the alkyl group has 1 to 8 carbon atoms, a vegetable oil (b), and a tackifier resin (c), wherein the content of the block copolymer (a) is 35-75 mass%, the content of the vegetable oil (b) is 10-50 mass%, and the content of the tackifier resin (c) is 5-40 mass% in terms of 100 mass% of the total of the components.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a hot-melt adhesive. More specifically, it is a hot-melt type that can be applied in a heat-melt state or a heat-softened state during application, and it relates to an adhesive that can form a protective sheet with an adhesive that can be attached to an adherend without the need for heating during use, that is, during pasting. Furthermore, the present invention relates to a protective sheet with an adhesive using the above hot-melt adhesive and a method for manufacturing the same.

Background Art

[0002] Simple head covers such as non-woven fabrics that can be easily removed may be attached to the head parts of seats on airplanes, trains such as the Shinkansen, buses, etc. As methods of attachment, in addition to using snap fasteners or strings, the use of a heat-weldable hot melt is mentioned (Patent Documents 1 and 2).

[0003] Also, in so-called open kitchens such as food supermarkets and restaurants, a partition may be provided between the kitchen and the sales floor / hall, and a simple protective (antifouling) sheet may be used to prevent soiling of the partition. As a method of attachment, the use of an adhesive is mentioned (Patent Document 3).

[0004] Furthermore, Patent Document 4 aims to provide an adhesive for forming an adhesive sheet that can be attached to an adherend typified by the surface of a headrest, the surface of a backrest, the surface of a seat, or a partition member in a kitchen without heating, and discloses a hot-melt adhesive containing a block copolymer, a liquid phosphorus-based flame retardant, a surfactant, and an adhesion-imparting resin.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

[0006] The hot-melt flame-retardant adhesive described in Patent Document 4 can be applied to a substrate without heating, but when applied to a painted surface where flame retardancy is not required, it can cause stains and lifting of the painted surface due to phosphorus-based flame retardants and surfactants, and furthermore, the painted surface may peel off when the adhesive is removed, making it unsuitable for certain substrates.

[0007] The present invention aims to provide an adhesive for forming adhesive protective sheets that can be attached to surfaces such as headrests, backrests, seats, and kitchen partitions without heating, and to provide an adhesive protective sheet. Furthermore, the invention aims to provide an adhesive protective sheet that can be applied without stringing, does not contaminate the painted surface to which it is attached, and can be easily replaced even after it becomes soiled. [Means for solving the problem]

[0008] To solve the above problems, the inventors conducted thorough research and found that they could obtain a hot-melt adhesive that can be applied without heating and can be easily and cleanly removed. In other words, the present invention relates to the following [1] to [7]. [1] A hot-melt adhesive comprising a block copolymer (A) of a polymer block containing structural units derived from an alkyl methacrylate with 1 to 3 C1 alkyl groups and a polymer block containing structural units derived from an alkyl acrylate with 1 to 8 C1 alkyl groups, a vegetable oil (B), and a tackifying resin (C), with the block copolymer (A) making up 35 to 75% by mass, the vegetable oil (B) making up 10 to 50% by mass, and the tackifying resin (C) making up 5 to 40% by mass of the total 100% by mass. [2] The hot-melt adhesive according to [1], wherein the mass ratio of alkyl methacrylate esters having 1 to 3 carbon atoms in the alkyl group in the block copolymer (A) is 10 to 55% by mass. [3] The hot-melt adhesive according to [1] or [2], wherein the melt flow rate of the block copolymer (A) at 190°C and a load of 2.16 kgf is 1 to 100 g / 10 min. [4] A hot-melt adhesive according to any one of [1] to [3], wherein the block copolymer (A) comprises at least one of the block copolymers of a block of methyl methacrylate and a block of n-butyl acrylate, and a block copolymer of a block of methyl methacrylate and a copolymer block of n-butyl acrylate and 2-ethylhexyl acrylate. [5] Furthermore, a hot melt adhesive according to any of [1] to [4] above, comprising a lubricant (D). [6] A protective sheet with adhesive, wherein an adhesive layer formed from a hot-melt adhesive according to any of [1] to [5] above is supported on at least a portion of one side of a sheet-like substrate. [7] A method for manufacturing an adhesive protective sheet, characterized by melting a hot-melt adhesive according to any of [1] to [5] above, and coating it onto at least a portion of one side of a sheet-like substrate to provide an adhesive layer. [Effects of the Invention]

[0009] The present invention provides an adhesive for forming adhesive-backed protective sheets and an adhesive-backed protective sheet that can be attached to surfaces such as headrests, backrests, seats, and kitchen partitions without heating. Furthermore, it provides an adhesive-backed protective sheet that can be applied without stringing, does not contaminate the painted surface to which it is attached, and can be easily replaced even after it becomes soiled. [Modes for carrying out the invention]

[0010] In this specification, numerical ranges specified using "~" include the numbers before and after "~" as the lower and upper limits. Furthermore, in this specification, block copolymer (A) of alkyl acrylate may be abbreviated as "block copolymer (A)", alkyl methacrylate with 1 to 3 carbon atoms in the alkyl group may be abbreviated as "alkyl methacrylate", and alkyl acrylate with 1 to 8 carbon atoms may be abbreviated as "alkyl acrylate".

[0011] <Block copolymer (A)> The block copolymer (A) contained in the hot-melt adhesive of the present invention is a block copolymer of a polymer block containing structural units derived from an alkyl methacrylate ester having 1 to 3 C1 of the alkyl group and a polymer block containing structural units derived from an alkyl acrylate ester having 1 to 8 C1 of the alkyl group.

[0012] Examples of block copolymers (A) include triblock polymers in which a hard segment (AH) formed from an alkyl methacrylate ester with 1 to 3 carbon atoms in the alkyl group and a soft segment (AS) formed from an alkyl acrylate ester with 1 to 8 carbon atoms in the alkyl group are bonded together as -AH-AS-AH-, and diblock polymers bonded together as -AS-AH-. Triblock polymers and diblock polymers may be used in combination.

[0013] The block copolymer (A) is clearly divided into a polymer portion of alkyl methacrylate with 1 to 3 C1 of the alkyl group (hard segment) and a polymer portion of alkyl acrylate with 1 to 8 C1 of the alkyl group (soft segment). By utilizing each polymer portion (segment), a hot-melt adhesive that achieves both heat resistance and low-temperature adhesion can be obtained. The hard segment enhances the cohesive force of the hot-melt adhesive, and by using the vegetable oil (B) and tackifying resin (C) described later in combination, the soft segment can be given wettability and adhesion to the adherend. Furthermore, by adding a lubricant (D), appropriate adhesion and ease of peeling can be provided.

[0014] As block copolymers, styrene-based elastomers are also known. However, since the block copolymer (A) of the present invention contains an ester bond, it has a higher polarity than styrene-based elastomers and is more likely to adhere to metals and glass.

[0015] In the block copolymer (A), the polymer portion of the alkyl methacrylate having 1 to 3 carbon atoms in the alkyl group, which is the hard segment in the block copolymer (A), is not plasticized by the vegetable oil (B) described later. Therefore, the sticking position does not shift or peel off, and even when the protective (antifouling) sheet is peeled off from the protected object, the surface of the protected object is not soiled.

[0016] As the alkyl methacrylate having 1 to 3 carbon atoms in the alkyl group for forming the hard segment of the block copolymer (A), methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and isopropyl methacrylate are preferable.

[0017] Assuming use in summer, from the viewpoint of enhancing the cohesive force at 40°C in order to maintain the adhesive force after 40°C over time and reduce the glue residue and contamination on the peeled surface after 40°C over time, methyl methacrylate is more preferable.

[0018] As the alkyl acrylate having 1 to 8 carbon atoms in the alkyl group for forming the soft segment of the block copolymer (A), methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, isoamyl acrylate, hexyl acrylate, and 2-ethylhexyl acrylate can be mentioned.

[0019] Furthermore, from the viewpoint of facilitating the compatibility of the adhesive force at 40°C and the adhesive force at -10°C, n-butyl acrylate, 2-ethylhexyl acrylate, or a combination thereof is preferable.

[0020] The mass ratio of the alkyl methacrylate having 1 to 3 carbon atoms in the block copolymer (A) is preferably 10 to 55% by mass. Alkyl acrylates have a lower glass transition temperature and are more fluid than alkyl methacrylates. In addition, they are more compatible with tackifying resins. Therefore, the lower the ratio of alkyl methacrylate and the higher the ratio of alkyl acrylate, the easier it is to wet the interface of the adherend, and the higher the adhesive strength. Within this range, it is possible to achieve adhesive strength, holding power, and reduced adhesive residue and contamination on the release surface over a wide temperature range from summer (40°C) to winter (-10°C). Block copolymer (A) in which the mass ratio of alkyl methacrylate ester with 1 to 3 carbon atoms in the alkyl group is 10 to 55% by mass is specifically Clarity LA2140E (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 20% by mass), Clarity LA2250 (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 30% by mass), Clarity LA2330 (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 20% by mass), Clarity LA3320 (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 15% by mass), Clarity LA3170 (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 12% by mass), Clarity LA2270 (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 40% by mass), Examples include Rarity LA4285 (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 50% by mass), Clarity LA1892 (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 52% by mass), Clarity LK9243 (MMA-(BA-2EHA)-MMA / triblock copolymer, MMA ratio: 17% by mass), Clarity KL-LK9333 (MMA-(BA-2EHA)-MMA / triblock copolymer, MMA mass ratio: 20% by mass), and these can be used individually or in combination.

[0021] Furthermore, from the viewpoint of initial adhesion, it is preferable that the mass ratio of alkyl methacrylate esters with 1 to 3 C1 alkyl groups be 40% by mass or less, specifically, Examples include Clarity LA2140E (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 20% by mass), Clarity LA2250 (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 30% by mass), Clarity LA2330 (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 20% by mass), Clarity LA3320 (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 15% by mass), Clarity LA3170 (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 12% by mass), Clarity LA2270 (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 40% by mass), Clarity LK9243 (MMA-(BA-2EHA)-MMA / triblock copolymer, MMA ratio: 17% by mass), and others. Each can be used individually or in combination. Furthermore, when a large amount of vegetable oil (B), described later, is added, it is preferable that the mass ratio of alkyl methacrylate esters with 1 to 3 carbon atoms in the alkyl group be 20% by mass or less. Specifically, Clarity LK9243 (MMA-(BA-2EHA)-MMA / triblock copolymer, MMA ratio: 17% by mass), Clarity LA2140E (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 20% by mass), Clarity LA2330 (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 20% by mass), Clarity LA3320 (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 15% by mass), Clarity LA3170 (MMA-BA-MMA / triblock copolymer, MMA mass ratio: 12% by mass), etc., are preferred because they can suppress the seepage of vegetable oil.

[0022] The melt flow rate (hereinafter referred to as MFR) of the block copolymer (A) of the present invention at 190°C and a load of 2.16 kgf is preferably 1 to 100 g / 10 min, and more preferably 1 to 100 g / 10 min. An MFR of 1 g / 10 min or more reduces stringing and improves coating properties. An MFR of 100 g / 10 min or less reduces the amount of adhesive remaining on the protected object even after the protective (anti-fouling) sheet is peeled off.

[0023] Furthermore, when using multiple types of block copolymers (A), only block copolymers (A) whose MFR falls within the above range may be used, or a combination of a block copolymer with a significantly high MFR and one with a low MFR may be used so that the overall MFR falls within the above range.

[0024] The block copolymer (A) is present in an amount of 35 to 75% by mass of the total 100% by mass of the block copolymer (A), vegetable oil (B), and tackifying resin (C). Below 35% by mass, the tackiness at -10°C decreases, making it prone to peeling in winter, while above 75% by mass, the heat meltability decreases, resulting in poor coating workability.

[0025] <Vegetable oil (B)> The hot-melt adhesive of the present invention contains vegetable oil (B), which allows for adjustment of the adhesive strength and suppression of the increase in adhesive strength when the protective film is adhered to a wall or the like for a long period of time. Furthermore, it significantly reduces the amount of adhesive residue left behind when the adhesive is removed.

[0026] Vegetable oil is sometimes classified into liquid vegetable oils and solid vegetable fats, both of which are extracted and refined from lipids contained in plants. However, both can be used as vegetable oil. Vegetable oils include coconut oil, corn oil, cottonseed oil, olive oil, palm oil, palm kernel oil, peanut oil, rapeseed oil, safflower oil, sesame oil, soybean oil, sunflower oil, almond oil, cashew oil, hazelnut oil, macadamia oil, mongongo oil, pecan oil, pine nut oil, pistachio oil, walnut oil, gourd seed oil, buffalo pumpkin oil, pumpkin seed oil, acai oil, blackcurrant oil, borage seed oil, evening primrose oil, amaranth oil, apricot kernel oil, argan oil, artichoke oil, avocado oil, babassu oil, moringa oil, borneo butter, Cape chestnut oil, cocoa butter, carob oil, koffeen oil, coriander seed oil, deka oil, linseed oil, flaxseed oil. Examples of suitable oils include grapeseed oil, hemp oil, kapok seed oil, larle manzia oil, meadowfoam oil, mustard oil, nutmeg butter, okra oil, papaya oil, perilla oil, pecu oil, pine nut oil, poppy oil, prune oil, quinoa oil, niger seed oil, rice oil, Royale oil, thatcha inchi oil, camellia oil, thistle oil, tomato oil, wheat oil, turnip oil, and grape oil, and are not particularly limited, but are preferably liquid at room temperature, have as little odor as possible, are resistant to heat degradation, and are also preferable to rice oil, which is a by-product generated during rice milling.

[0027] In the total 100% by mass of the block copolymer (A), vegetable oil (B), and tackifying resin (C), the vegetable oil (B) is contained at a concentration of 10 to 50% by mass. Below 10% by mass, the increase in tackiness over time cannot be suppressed, resulting in a large amount of adhesive residue on the release surface and decreased tackiness at low temperatures. Above 50% by mass, the cohesive force decreases, reducing tackiness retention, which may cause oil stains on the release surface, or damage to the release coating surface, causing it to peel off or discolor. <Tackifying resin (C)> In the present invention, the tackifying resin (C) can further improve the initial and long-term adhesive strength. Examples of the tackifying resin (C) include phenolic resins, modified phenolic resins, terpene resins, terpene phenolic resins, xylene phenolic resins, xylene resins, cyclopentadiene-phenolic resins, aliphatic and aromatic petroleum resins, phenol-modified petroleum resins, rosin esters, hydrogenated rosin esters, low molecular weight polystyrene resins, and terpene resins. The tackifying resin may be used alone or in combination of two or more types.

[0028] In a total of 100% by mass of block copolymer (A), vegetable oil (B), and tackifying resin (C), the tackifying resin (C) is present in an amount of 5 to 40% by mass. Below 5% by mass, the tackiness is weak, and above 40% by mass, the tackiness becomes too strong, making it prone to leaving adhesive residue.

[0029] <Lubricant (D)> The hot-melt adhesive of the present invention may further contain a lubricant (D) to the extent that it does not impair the objective of the invention, for purposes such as improving peelability and slipperiness, and improving blocking and stain prevention. Examples of lubricant (D) include fatty acid amide compounds, alkylene fatty acid amide compounds, metal soap compounds, and fatty acid ester compounds.

[0030] Examples of fatty acid amide-based and alkylene fatty acid amide-based lubricants include, Aliphatic monocarboxylic acid amides such as lauric acid amide, palmitic acid amide, oleic acid amide, stearic acid amide, erucic acid amide, behenic acid amide, ricinoleic acid amide, and hydroxystearic acid amide, N-substituted aliphatic monocarboxylic acid amides such as N-oleyloleamide, N-oleyl stearate, and N-stearyloleamide, Aliphatic biscarboxylic acid amides such as methylenebisstearamide and ethylenebisstearamide, Examples include N,N'-ethylene-bis-oleylamide, N,N'-ethylenebisstearamide, and N,N'-methylenebisstearamide.

[0031] Examples of metal soap-based lubricants include, Examples include metal salts of higher fatty acids such as calcium stearate, magnesium stearate, barium stearate, zinc stearate, aluminum stearate, lithium stearate, calcium lauryl latate, magnesium lauryl latate, barium lauryl latate, zinc lauryl latate, aluminum lauryl latate, and lithium lauryl latate.

[0032] Fatty acid ester lubricants are those in which one or more fatty acids are esterified to an alcohol.

[0033] As the alcohol, monohydric or polyhydric alcohols can be used. The monohydric alcohol is preferably a higher alcohol having 6 or more carbon atoms, and more preferably a higher alcohol having 10 or more carbon atoms. Examples include mystyryl alcohol, stearyl alcohol, and oleyl alcohol. Examples of polyhydric alcohols include dihydric alcohols or alcohols with three or more hydric values. Examples of dihydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, and 1,6-hexanediol. Examples of trihydric or higher alcohols include glycerin, diglycerin, triglycerin, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, mannitol, and sorbitol. Preferably, the materials are glycerin, propylene glycol, pentaerythritol, and dipentaerythritol, and more preferably, glycerin and dipentaerythritol.

[0034] Examples of fatty acids include, Saturated fatty acids such as caproic acid, caprylic acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, palmitic acid, stearic acid, behenic acid, lignosenoic acid, cerotic acid, montanic acid, and melissic acid. Unsaturated fatty acids such as oleic acid, elaidic acid, linoleic acid, linolenic acid, arachidonic acid, prasidic acid, erucic acid, and ricinoleic acid. Examples include hydroxy fatty acids such as 12-hydroxystearic acid, and aliphatic dicarboxylic acids such as adipic acid. Among these, myristic acid, palmitic acid, stearic acid, 12-hydroxystearic acid, and oleic acid are preferred. Particularly preferred are stearic acid or triglycerides of 12-hydroxystearic acid.

[0035] These lubricants may be used individually or in combination of two or more types. The amount of lubricant added is preferably 0.01 to 10% by mass relative to 100% by mass of the total of the block copolymer (A), vegetable oil (B), and tackifying resin (C). This allows for good release properties, slipperiness, anti-blocking properties, and anti-fouling properties without reducing adhesive strength or retention. From the viewpoint of processability, it is more preferably 0.03 to 5% by mass.

[0036] The hot-melt adhesive of the present invention may contain additives such as antioxidants, ultraviolet absorbers, light stabilizers, antibacterial agents, deodorizers, fragrances, and flame retardants, to the extent that they do not impair the purpose of the invention.

[0037] Examples of the above-mentioned antioxidants include pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, diethyl[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate, 4,6-bis(octylthiomethyl)-o-cresol, ethylenebis(oxyethylene)bis[3-(5-t-butyl-4-hydroxy-m-tolyl)propionate, tris(2,4-di-t-butylphenyl)phosphite, and bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite. These may be used individually or in combination of two or more.

[0038] The phenolic antioxidants described above function as radical trappers by stabilizing ROO· (peroxy radicals) generated during the autooxidation chain growth process by donating hydrogen, and then becoming stable phenoxy radicals protected by ortho substituents to halt the chain reaction, thereby effectively suppressing thermal degradation of the resin composition. In particular, combining phenolic antioxidants with lactone-based antioxidants or vitamin E-based antioxidants, which exhibit a faster radical trapping reaction than phenolic antioxidants, yields even better results. Furthermore, the phosphorus-based antioxidants described above have the function of non-radically decomposing peroxides and ROOH, thereby halting the chain reaction in the autooxidation process, and effectively suppressing thermal degradation of the resin composition.

[0039] The above-mentioned UV absorbers are not particularly limited and include commonly used ones such as salicylic acid-based, benzophenone-based, and benzotriazole-based agents. These may be used alone or in combination of two or more types.

[0040] Examples of commonly used light stabilizers include hindered amine-based types.

[0041] The method for producing the hot-melt adhesive of the present invention is not particularly limited, but it is preferable to heat and mix the above (A), (B), (C), (D), etc. using a melting vessel equipped with a roll, a Banbury mixer, a kneader, or a stirrer.

[0042] <Adhesive protective sheet> The adhesive protective sheet of the present invention has an adhesive layer formed from the hot-melt adhesive of the present invention supported on at least a portion of one side of a sheet-like substrate. It is preferable to cover the surface side of the adhesive layer with a release sheet until it is applied.

[0043] Examples of sheet-like substrates include nonwoven fabrics and polyethylene terephthalate films. Examples of release sheets include polyethylene terephthalate (hereinafter also referred to as PET) sheets coated with a release agent such as silicone.

[0044] An adhesive protective sheet may have an adhesive layer provided on at least a portion of one side of a sheet-like substrate, or it may have an adhesive layer provided on the entire surface. If an adhesive layer is to be applied to the entire surface, from a cost perspective, the adhesive should be 30g / m². 2 The following is preferable, 20g / m 2 The following is even more preferable.

[0045] <Method for manufacturing adhesive protective sheets> The adhesive protective sheet of the present invention can be obtained by melting the aforementioned hot-melt type adhesive and applying it to at least a portion of one side of a sheet-like substrate to form an adhesive layer. Alternatively, the adhesive protective sheet of the present invention can also be manufactured by melting the hot-melt adhesive of the present invention described above, coating it on at least a portion of the release surface of a release sheet, quickly stacking the sheet-like substrates on top of each other, and pressing them together with a pressure roll. Further, the protective sheet with an adhesive of the present invention may be obtained by melting the above-described hot-melt adhesive, applying it to a release roll such as a silicon roll, transferring it to a sheet-like base material, and then covering the surface with a release sheet.

[0046] Examples of the device for heating and melting the hot-melt adhesive and applying it include, but are not particularly limited to, a gravure coater, a roll coater, a die coater, a slit coater, etc.

Examples

[0047] Hereinafter, the present invention will be specifically and detailedly described with reference to examples. However, these examples are merely one aspect of the present invention, and the present invention is not limited by these examples. In the examples, "parts" represents "parts by mass", and "%" represents "% by mass".

[0048] [MFR] It was measured in accordance with JIS.K7210.

[0049] (Example 1) In a kneader equipped with a stirrer, 38 parts of A1 (manufactured by Kuraray Co., Ltd.; Clarite LK9243) as the block copolymer (A), 38 parts of B1 (rice oil) as the vegetable oil (B), and 24 parts of C2 (manufactured by Clayton Chemical Co., Ltd.; Silverace SA140) as the tackifier resin (C) were added, and stirred at 180 °C for 3 hours to obtain a hot-melt adhesive. The obtained hot-melt adhesive was evaluated according to the method described below.

[0050] (Examples 2 to 41), (Comparative Examples 1 to 11) Hot-melt adhesives of Examples 2 to 41 and Comparative Examples 1 to 11 were obtained in the same manner as in Example 1, except that the number of parts shown in Tables 1 to 3 was changed. The obtained hot-melt adhesives were evaluated according to the method described below.

[0051] The abbreviations of the block copolymer (A), etc. described in Tables 1 to 3 are shown below. (A1): A triblock copolymer of methyl methacrylate with a methyl methacrylate content of 17% by mass, and a mixture of butyl acrylate and 2-ethylhexyl acrylate (manufactured by Kuraray Co., Ltd.; Clarity LK9243 (MMA-(BA / 2EHA)-MMA / triblock copolymer, MFR: 93g / 10 min)) (A2) A triblock copolymer of methyl methacrylate and n-butyl acrylate containing 20% ​​by mass of methyl methacrylate (Kuraray Co., Ltd.; Clarity LA2330 (MMA-BA-MMA / triblock copolymer, MFR: 3.7g / 10 min)) (A3): A triblock copolymer of methyl methacrylate and n-butyl acrylate containing 30% by mass of methyl methacrylate (Kuraray Co., Ltd.; Clarity LA2250 (MMA-BA-MMA / triblock copolymer, MFR: 25g / 10 min)) (A4): A triblock copolymer of methyl methacrylate and n-butyl acrylate, with a methyl methacrylate content of 52% by mass (Kuraray Co., Ltd.; Clarity LA1892 (MMA-BA-MMA / triblock copolymer, MFR: 11.4g / 10min)) (A'1): A hard-segment-soft-segment-hard-segment triblock copolymer consisting of a styrene hard segment with a styrene content of 19% by mass and an isoprene soft segment (manufactured by Kraton; Kraton D-1160, MFR: 5~13g / 10 min)

[0052] The notation for vegetable oils listed in Tables 1-3 is shown below. (B1): Rice oil (B2): Safflower oil (B3): Soybean oil (soybean oil) (B4): Sunflower oil (B5): Cotton oil (cottonseed oil) (B6): Rapeseed oil (B7): Grape oil (B8): Corn oil

[0053] The notation for plasticizers listed in Table 3 is shown below. (B'1): BDP (ADEKA Corporation; ADEKA Stab FP-600: Bisphenol A diphenyl phosphate) (B'2): DOP (manufactured by Hachidai Chemical Industry Co., Ltd.; bis(2-ethylhexyl) phthalate) (B'3): PL012 (manufactured by Riken Vitamin Co., Ltd.; Rikemar PL012: glycerin acetlaurate)

[0054] The abbreviations for the tackifying resin (C) listed in Tables 1-3 are shown below. (C1): Pencel D160 (manufactured by Arakawa Chemical Industries; rosin ester, softening point 160°C) (C2): Silveres SA140 (manufactured by Kraton Chemical; α-methylstyrene resin, softening point 140°C) (C3): Haritack FK125 (manufactured by Harima Chemicals Co., Ltd.; acid-modified rosin, softening point 128°C) (C4): Quinton G115 (manufactured by Nippon Zeon; petroleum-based aliphatic / aromatic copolymer, softening point 115°C) (C5): YS Polystar T115 (manufactured by Yasuhara Chemical Co., Ltd.; terpene phenol resin, softening point 115℃) (C6): Pencel GA100 (manufactured by Arakawa Chemical Industries; rosin ester, softening point 100°C) (C7): Silverless SA100 (manufactured by Kraton Chemical; α-methylstyrene resin, softening point 100°C) (C8) Quinton A100 (manufactured by Nippon Zeon Corporation; petroleum-based aliphatic hydrocarbon, softening point 100°C) (C9): RHR301 (manufactured by Nissei Rinsan Kako Co., Ltd.; hydrogenated rosin, softening point 72°C)

[0055] The abbreviations for lubricants (D) listed in Tables 1-3 are shown below. (D1): Amid E (Aliphatic amide, manufactured by Kao Corporation)

[0056] <Suitability for coating> The coating condition of a hot-melt adhesive applied to a 25 μm thick release PET sheet using a roll coater at a coating temperature of 160°C and a speed of 20 m / min was visually evaluated. ◎: No stringing whatsoever, uniform application: Good ○: There are 1-3 places where the product is stringy, but the application is uniform: Usable ×: There are four or more places where the product is stringy and the application is uneven: Not usable.

[0057] [Preparation of test samples] Using a roll coater, the hot-melt adhesives of Examples 1-20 and Comparative Examples 1-11 were applied to 25 μm peelable PET at a coating temperature of 160°C and a speed of 20 m / min. Immediately afterward, a nonwoven fabric was bonded to the surface, and the samples were left for 24 hours under conditions of 23°C and 65% humidity (hereinafter 65% RH). After that, the samples were cut to a size of 100 mm x 25 mm to be used as test specimens.

[0058] <Oil stain> The prepared test samples were peeled off using release PET, and the oil floating on the adhesive surface and the oil stains remaining on the release PET were visually observed and evaluated. ◎: No oil stains whatsoever, even application: Good ○: There are 1-5 oil stains, but the application is uniform: Usable ×: If there are 6 or more oil stains, or if the application is uneven: Not usable. <Low-temperature adhesive strength> The peelable PET was removed from the prepared test samples, and each test sample was attached to the entire surface of a SUS plate slightly larger than the test sample. The plates were then pressed together twice using a 2kg load roller, left for 1 hour, and then peeled 180° at a speed of 200mm / min in a -10°C environment. The strength at that time was measured. ◎: 0.03N / 25mm or more and 6N / 25mm or less: Good ○: Over 6N / 25mm and up to 9N / 25mm: Usable ×: Less than 0.03N / 25mm or greater than 9N / 25mm: Not usable <Initial adhesive strength> The peelable PET was removed from the prepared test samples, and each test sample was attached to the entire surface of a SUS plate slightly larger than the test sample. The plates were then pressed together twice using a 2kg load roller, left for 1 hour, and then peeled 180° at a speed of 200mm / min in an environment of 23°C and 65%RH, and the strength at that time was measured. ◎: 0.03N / 25mm or more and 6N / 25mm or less: Good ○: Over 6N / 25mm and up to 9N / 25mm: Usable ×: Less than 0.03N / 25mm or greater than 9N / 25mm: Not usable

[0059] <Heat resistance test> The release PET was peeled off the prepared test samples, and each test sample was attached to the entire surface of a SUS plate slightly larger than the test sample, and pressed down once back and forth with a 2kg load roller. Then, each test sample was placed face down in a 40°C oven and left for one month, and the adhesion and fall conditions were observed. ◎: No detachment, no peeling: Good condition ○: Peeling area less than 10%: Usable ×: More than 10% of the surface area is detached or peeled: Not usable. Furthermore, for items that showed "×: detachment or peeling" in the heat resistance test, the adhesive strength after the heat resistance test and the adhesive residue after peeling could not be evaluated, so they are marked with "-" in Table 4.

[0060] <Adhesive strength after heat resistance test> After the heat resistance test described above, the samples were left to stand for 2 hours in an atmosphere of 23°C and 65% RH. Then, a peel test was performed under the same conditions as for the initial adhesion test, and the peel strength was evaluated according to the following criteria. ◎: 0.03N / 25mm or more and 6N / 25mm or less: Good ○: Over 6N / 25mm and up to 9N / 25mm: Usable ×: Less than 0.03N / 25mm or greater than 9N / 25mm: Not usable

[0061] <Adhesive residue after peeling> When measuring the adhesive strength after the heat resistance test described above, the state of adhesion of the adhesive to the SUS plate, which was the adherend, was observed visually. ◎: No transfer of hot melt adhesive whatsoever. : Good ○: Less than 10% of the application area was affected by transfer, but it could be easily removed by hand. : Usable ×: Transfer is observed covering more than 10% of the application area, or the transfer is 10% or less, but the adhesive cannot be removed by hand. : Not usable.

[0062] <Contamination of painted surfaces> The test sample was bonded to a commercially available marble-patterned tile and stored in a 40°C oven for 3 months. After 3 months of storage, it was left at room temperature for 1 hour, then the test sample was peeled off the marble-patterned tile, and the condition of the painted surface of the marble-patterned tile where it had been peeled off was observed. ◎: No stains, paint peeling or lifting, good condition. ○: No paint lifting or peeling, but stains are present: Usable ×: Paint peeling or lifting occurs: Unusable

[0063] As shown in Tables 1-3, the hot-melt adhesive of the present invention can be uniformly coated onto release PET, and even when a nonwoven fabric is attached to the coated surface and the release PET is peeled off, there is no oil stain. When applied to a SUS plate, it exhibits excellent adhesion at low temperatures and heat resistance, and even after a heat resistance test, the adhesion does not decrease sufficiently, and there is no adhesive residue when peeled off. In other words, it is now possible to provide an adhesive for forming adhesive protective sheets and adhesive protective sheets that can be attached to surfaces such as headrests, backrests, seats, and kitchen partitions without heating. Furthermore, it is possible to provide adhesive protective sheets that can be applied without stringing, do not contaminate the painted surface to which they are attached, and can be easily replaced even after becoming soiled.

[0064] [Table 1]

[0065] [Table 2]

[0066] [Table 3]

Claims

1. The block copolymer (A), vegetable oil (B), and tackifying resin (C) comprise 100% by mass of a total polymer block containing structural units derived from alkyl methacrylate with 1 to 3 C1 alkyl groups and a polymer block containing structural units derived from alkyl acrylate with 1 to 8 C1 alkyl groups, with 35 to 75% by mass of block copolymer (A), 10 to 50% by mass of vegetable oil (B), and 5 to 40% by mass of tackifying resin (C). A hot-melt adhesive in which vegetable oil (B) is liquid at room temperature.

2. The hot-melt adhesive according to claim 1, wherein the mass ratio of alkyl methacrylate esters having 1 to 3 carbon atoms in the alkyl group in the block copolymer (A) is 10 to 55% by mass.

3. The hot-melt adhesive according to claim 1, wherein the melt flow rate of the block copolymer (A) at 190°C and a load of 2.16 kgf is 1 to 100 g / 10 min.

4. The hot-melt adhesive according to claim 1, wherein the block copolymer (A) comprises at least one of the following: a block copolymer of a block of methyl methacrylate and a block of n-butyl acrylate, and a block copolymer of a block of methyl methacrylate and a copolymer block of n-butyl acrylate and 2-ethylhexyl acrylate.

5. Furthermore, the hot-melt adhesive according to claim 1, further comprising a lubricant (D).

6. A protective sheet with adhesive, wherein at least a portion of one side of a sheet-like substrate is supported with an adhesive layer formed from a hot-melt adhesive according to any one of claims 1 to 5.

7. A method for manufacturing an adhesive-coated protective sheet, characterized by melting a hot-melt adhesive according to any one of claims 1 to 5, coating it on at least a portion of one side of a sheet-like substrate, and thereby providing an adhesive layer.

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