Hot melt adhesive and filter assembled with said adhesive

Abstract

This adhesive is a hot-melt adhesive satisfying the following conditions (A), (B), and (C). (A) Conformance to ASTM D3236-73, and the melting viscosity measured at 190℃ using a No. SC4-27 spindle is 1,000-15,000 mPa·s. (B) Conformance to JIS K6863-1994, and the softening point measured using silicone oil as a heat medium is 130-170℃. (C) Conformance to JIS K7196-1991, and when a cylindrical detection rod with a diameter of 3 mm is set on a specimen cut out in a 5-mm square from a sample sheet molded at a thickness of 2 mm, nitrogen gas is flowed over the specimen at a rate of 100 ml / min, a load of 10 gf is applied to the specimen, and the temperature of the specimen is ramped up at a speed of 5℃ / min, the specimen softens and displacement thereof in the contraction direction reaches 0.05 mm at a temperature of at least 90℃.

Description

[Technical Field]

[0001] The present invention relates to a filter assembly adhesive, and more particularly to a hot melt adhesive for use in air filters made by pleating filter media. Air filters constructed in accordance with the present invention are particularly useful for purifying the air inside automobiles. [Background technology]

[0002] It is well known to use a filter made by pleating a filter material such as a nonwoven fabric to allow air or other fluids to pass through and remove dust particles and the like. The reason for pleating the filter material is to maximize the filter area for the passing fluid, and for this purpose, it is preferable to have higher pleats and a larger number of pleats. However, increasing the pleat height or number of pleats causes the pleats to deform due to the pressure of the passing fluid, making them more likely to come into contact with each other. The contact between pleats reduces the filtration area of ​​the filter, reduces breathability, and causes a large pressure loss, thereby causing a decrease in filter performance. Therefore, it is necessary to prevent pleat contact.

[0003] In order to prevent pleats from contacting each other, a method has been proposed in which a line of hot melt adhesive is applied to the top of the pleats in a direction transverse to the direction in which the pleats extend, and then the adhesive is allowed to harden, thereby preventing the tops of adjacent pleats from contacting each other (hereinafter also referred to as "top bonding"). Regarding the top adhesive, various methods for improving it have been proposed, such as the following. For example, a method has been disclosed in which a foamable resin is used as a hot melt adhesive to provide flexibility to the adhesive between the pleats of a pleated filter medium, in order to arrange the pleats in an orderly manner and obtain a filter that is less likely to lose its shape (Patent Document 1). Furthermore, a sticking prevention member has been disclosed, which is made of a hot melt adhesive whose surface layer has lower crystallinity than the interior, and which can reliably prevent the pleats from sticking together and from falling off due to vibration, etc. (Patent Document 2).

[0004] As such, hot melt adhesives play an extremely important role in preventing the pleats of pleated filter media from touching each other, and their compositions include ethylene / vinyl acetate (EVA) adhesives, polyethylene adhesives, polypropylene adhesives, polyethylene / polypropylene adhesives, and polyester adhesives. Although polypropylene, which is difficult to bond, is sometimes used as the filter media for filters, this filter media is a porous nonwoven fabric, and so it is possible to bond it with polyester or polyamide adhesives, which are normally difficult to bond to polypropylene, due to the anchoring effect.

[0005] However, these hot melt adhesive compositions have low flexibility, making it difficult to process them as intended. Increasing flexibility makes the filter more susceptible to deformation at higher temperatures than the normal filter environment (-20 to 80°C). To prevent deformation at these temperatures, a hot melt adhesive with a high softening point is used. In this case, there is a problem that a low coating temperature increases the viscosity, which requires a high coating temperature. For example, if a hot melt adhesive is applied at a coating temperature of 180°C or higher to achieve a low viscosity that can be applied in industrial production processes, if the filter medium is polypropylene, the coating temperature of 180°C may cause the polypropylene filter medium to deform. If the coating temperature is lowered to avoid deformation of the polypropylene filter medium, the viscosity of the hot melt adhesive will become too high, making it impossible to apply the hot melt adhesive stably. As a hot melt adhesive that solves these problems, a hot melt adhesive containing a copolymer of 1-butene and another olefin, polypropylene wax, and a tackifying resin as constituent components has been proposed (Patent Document 3).

[0006] This hot melt adhesive composition has a low melt viscosity and little temperature dependency of the melt viscosity, so the adhesive can be applied to the filter material at a low application temperature, and can also be applied to heat-sensitive filter material, preventing the pleats from losing their shape even in high normal environmental temperatures. However, this hot melt adhesive has limited heat resistance, and when exposed to a temperature environment of around 80°C (hereinafter referred to as a "high temperature environment"), which simulates the temperature inside a car left outdoors, the surface of the hot melt adhesive becomes sticky, and even a slight stress on the filter can cause the hot melt adhesive applied between the pleats to stick together, causing the pleats to come into contact with each other. In particular, when a base material with high repulsive force is used as the filter material, the stress of returning the pleated material to its original flat state is strong, and if this stress exceeds the cohesive strength of the solidified hot melt adhesive attached to the top, peeling of the hot melt adhesive can be accelerated.

[0007] On the other hand, pleated filter media are used as filters by fitting them into a frame made up of end plates arranged around the periphery. In order to fix the filter media within the frame, the end faces in the direction in which the pleats of the filter extend, and, if necessary, both parallel side ends perpendicular to the direction in which the pleats of the filter media extend, are glued to the end plates of the frame (hereinafter, also referred to as "end gluing").

[0008] When forming a filter by performing both the end bonding process, in which the pleated filter material is bonded to the frame, and the top bonding process, in which a line of hot melt adhesive is applied to the top of the pleats and allowed to solidify, either process can be performed first.

[0009] As adhesives for edge bonding, for example, olefin-based or ethylene vinyl acetate-based hot melt adhesives with relatively low melting temperatures have been proposed to prevent the filter medium from melting (Patent Document 4). However, in the case of edge bonding, the contact area between the filter medium and the end plate is small, making it difficult to obtain sufficient adhesive strength, and these hot melt adhesives have sometimes peeled off when subjected to stress such as vibration or in high-temperature environments. In particular, when a base material with high resilience is used as the filter medium, the stress to return to its original flat state after pleating is strong, and when this stress exceeds the cohesive strength of the solidified hot melt adhesive attached to the edge, peeling from the pleat surface can be accelerated. A polyamide-based hot melt adhesive has been proposed for the purpose of improving the sealing property between the filter medium and the end plate of the frame and having excellent pressure resistance (Patent Document 5).

[0010] However, although the polyamide-based hot melt adhesive of Patent Document 5 has high heat resistance in high-temperature environments, the resin is prone to oxidative degradation and carbonization during heating and melting during application, and this carbonization can enter the filter media as foreign matter from the nozzle of the application device, reducing productivity. In addition, there is a problem that a large amount of carbonization clogs the nozzle of the application device, making it impossible to obtain the desired application amount, resulting in a decrease in the strength of the filter. Furthermore, in terms of manufacturing process management, it is troublesome to use two different hot melt adhesives for top bonding and edge bonding, and there has been a demand for a hot melt adhesive that can be used in both processes. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 7-47211 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-65170 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-226561 [Patent Document 4] Japanese Patent Application Publication No. 5-103936 [Patent Document 5] Japanese Patent Application Publication No. 10-272329 Summary of the Invention [Problem to be solved by the invention]

[0012] One embodiment of the present invention aims to provide a hot melt adhesive that can be applied at a low application temperature for top bonding, has low viscosity during application, and maintains adhesive strength even in high temperature environments, and that has strong adhesive strength for end bonding between end plates and filter media for edge bonding, making it usable for both types of bonding. [Means for solving the problem]

[0013] As a result of extensive research into solving the above problems, the present inventors have found that a hot melt adhesive that satisfies the following conditions can solve these problems, and have completed the present invention. Furthermore, they have found that the hot melt adhesive can be suitably used as an air filter, particularly an air filter for use in an automobile interior, because it has the above properties, and have completed the present invention. The present invention includes the following embodiments. [1] (A) The melt viscosity at 190°C measured in accordance with ASTM D3236-73 using Spindle No. SC4-27 is 1,000 mPa·s or more and 15,000 mPa·s or less; (B) The softening point measured in accordance with JIS K6863-1994 using silicone oil as a heat medium is 130°C or higher and 170°C or lower, (C) In accordance with JIS K7196-1991, a cylindrical detection rod with a diameter of 3 mm is placed on a test piece cut into a 5 mm square from a sample sheet molded to a thickness of 2 mm. Nitrogen gas is flowed at a rate of 100 ml / min, a load of 10 gf is applied, and the temperature is raised at a rate of 5°C / min. When the test piece softens and the displacement in the shrinking direction becomes 0.05 mm, the temperature is 90°C or higher. A hot melt adhesive characterized by: [2] (D) In ​​accordance with JIS K6850-1999, a hot melt adhesive melted at 180°C was applied in the form of a 4-5mm bead to the 10mm x 25mm adhesive area at one end of a 100mm x 25mm polypropylene plate, and within 5 seconds, one end of another polypropylene plate was placed over the adhesive area and pressed with a pressure of 24kgf for 5 seconds to form a test piece. The test piece was left at 25°C for 16 hours, and then the adhesive strength when both polypropylene plates of the test piece were pulled in opposite directions at 80°C at a rate of 50mm / min was 15N / cm. 2 That's all, (E) A hot melt adhesive according to [1], in which when one end of the test piece is fixed vertically to a jig in a constant temperature bath, a 500 g weight is attached to the other end, and the test piece is left standing at 38°C for 15 minutes, and then the temperature is raised at a rate of 0.4°C / min, the adhesive part can no longer withstand the load of the weight and the weight falls, and the temperature reaches 90°C or higher. [3] The hot melt adhesive according to [1] or [2], which contains a polyolefin. [4] The hot melt adhesive according to [3], wherein the polyolefin is polypropylene. [5] The hot melt adhesive according to any one of [1] to [4], further comprising an antioxidant. [6] A hot melt adhesive according to any one of [1] to [5], which is used in assembling a filter consisting of pleated filter material and a frame surrounding the filter material, to prevent the pleats from contacting each other by being placed between adjacent pleats, and / or to bond the filter material to the frame. [7] The hot melt adhesive according to [6], wherein the filter material is made of polypropylene nonwoven fabric. [8] The hot melt adhesive according to [6] or [7], wherein the filter is an air filter for use in an automobile cabin. [9] A filter having pleated filter material and a frame surrounding the filter material as constituent parts, assembled using the hot melt adhesive described in any one of [1] to [7].

[10] An air filter for use in an automobile cabin, which is constructed by assembling a pleated filter material and a frame surrounding the filter material using the hot melt adhesive described in any one of [1] to [8]. [Effects of the Invention]

[0014] The hot melt adhesive of the present disclosure can be applied at a low application temperature of 180°C or less, and has low viscosity during application, resulting in good application workability. It also maintains adhesive strength even in high-temperature environments, making it suitable for use in high-temperature environments. Furthermore, it can be used for both top and edge bonding, making it suitable for use in filter applications, particularly automotive air filters. DETAILED DESCRIPTION OF THE INVENTION

[0015] A first aspect of the present invention (the hot melt adhesive of the present disclosure) is a hot melt adhesive that satisfies the following conditions (A), (B), and (C). (A) The melt viscosity at 190°C measured in accordance with ASTM D3236-73 using Spindle No. SC4-27 is 1,000 mPa·s or more and 15,000 mPa·s or less. (B) The softening point measured in accordance with JIS K6863-1994 using silicone oil as a heat medium is 130°C or higher and 170°C or lower. (C) In accordance with JIS K7196-1991, a cylindrical detection rod with a diameter of 3 mm is placed on a test piece cut into a 5 mm square from a sample sheet molded to a thickness of 2 mm. Nitrogen gas is flowed at a rate of 100 ml / min, a load of 10 gf is applied, and the temperature is raised at a rate of 5°C / min. When the test piece softens and the displacement in the shrinkage direction becomes 0.05 mm, the temperature must be 90°C or higher. A hot melt adhesive that satisfies the above conditions (A), (B), and (C) is easy to apply and has good adhesion to the substrate. When used in filter applications, it is easy to apply to the filter medium, has good adhesion between the filter medium and the end plate, and is prevented from peeling or falling off even when subjected to forces such as vibration or bending stress. The melt viscosity of (A) is more preferably 2,000 mPa·s or more and 10,000 mPa·s or less. The softening point of (B) is more preferably 135°C or higher and 165°C or lower. Furthermore, the temperature at which the test piece in (C) softens and the displacement in the shrinking direction becomes 0.05 mm is more preferably 100° C. or higher.

[0016] In one embodiment of the present invention, the hot melt adhesive is a hot melt adhesive that further satisfies the following conditions (D) and (E). (D) In ​​accordance with JIS K6850-1999, a hot melt adhesive melted at 180°C was applied in the form of a 4-5mm bead to the 10mm x 25mm adhesive area at one end of a 100mm x 25mm polypropylene plate, and within 5 seconds, one end of another polypropylene plate was placed over the adhesive area and pressed with a pressure of 24kgf for 5 seconds to form a test piece. The test piece was left to stand at 25°C for 16 hours, and then the adhesive strength when both polypropylene plates of the test piece were pulled in opposite directions at 80°C at a rate of 50mm / min was 15N / cm. 2 (E) When one end of the test piece is fixed vertically to a jig in a constant temperature bath, a 500 g weight is attached to the other end, and the test piece is left standing at 38°C for 15 minutes, and then the temperature is raised at a rate of 0.4°C / min, the adhesive part can no longer withstand the load of the weight and the weight falls, and the temperature reaches 90°C or higher. Hot melt adhesives that satisfy the above conditions (D) and (E) have good adhesion, particularly when polypropylene is used as the adherend, and excellent durability in high-temperature environments. When used with filter media made of polypropylene nonwoven fabric, they provide good adhesion between the filter media and end plates and prevent peeling or falling off even when the filter is placed in a high-temperature environment. The adhesive strength in (D) is 30 N / cm 2 The above is even more preferable.

[0017] In one embodiment of the present invention, the hot melt adhesive further comprises a polyolefin. In the present invention, "polyolefin" refers to a polymer of an olefin preferably having 2 to 4 carbon atoms, and either amorphous or crystalline polyolefins can be used. The polyolefin includes olefin homopolymers, copolymers, and mixtures thereof. Examples of such polyolefins include polyethylene, polypropylene, copolymers of ethylene and propylene, copolymers of propylene and 1-butene, copolymers of ethylene and 1-butene, and copolymers of propylene, ethylene, and 1-butene, which can be used alone or in combination. Furthermore, polypropylene is preferred as the polyolefin because of its heat-resistant adhesiveness, and polypropylene is preferably contained in an amount of 50 mass % or more of the total polyolefin.

[0018] Here, the number average molecular weight of the polyolefin is not particularly limited as long as it exhibits the performance aimed at in the present invention, but is preferably 2,000 to 30,000, more preferably 4,000 to 25,000, and even more preferably 6,000 to 25,000. The glass transition temperature (hereinafter, in this specification, "glass transition temperature" refers to the arithmetic mean temperature of the glass transition onset temperature and the glass transition end temperature measured by DSC using a method similar to that described in DIN 53765) is preferably -20 to -40°C. In the hot melt adhesive of the present disclosure, the polyolefin content is preferably 70 to 99 mass %, more preferably 75 to 99 mass %, and even more preferably 80 to 99 mass %.

[0019] In one embodiment of the present invention, the hot melt adhesive contains polypropylene as the constituent polyolefin. More preferably, it is amorphous polypropylene. The polypropylene imparts adhesive properties to the hot melt adhesive composition and reduces the viscosity during application. Any known polypropylene can be used, but copolymers of ethylene and propylene, copolymers of propylene and 1-butene, and copolymers of propylene, ethylene, and 1-butene can also be used.

[0020] The number-average molecular weight of the polypropylene is not particularly limited as long as it exhibits the performance desired by the present invention, but is generally preferably 4,000 to 25,000, more preferably 6,000 to 15,000. The melt viscosity at 190°C is preferably 1,500 to 50,000 mPa·s, more preferably 1,500 to 30,000 mPa·s. The glass transition temperature is preferably −20°C to −40°C.

[0021] In one embodiment of the present invention, the hot melt adhesive further comprises an antioxidant. The antioxidant is not particularly limited, and known antioxidants can be used, and examples thereof include phenol-based antioxidants, amine-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, hydroquinone-based antioxidants, quinoline-based antioxidants, hydrazines, and urea-based antioxidants. Among these, phenol-based antioxidants and sulfur-based antioxidants are preferred because they have stable melt viscosity and are less likely to discolor when heated, and among the phenol-based antioxidants, hindered phenol-based antioxidants are more preferred.

[0022] Examples of phenolic antioxidants include 2,6-di-t-butyl-p-cresol (BHT), 2,2'-methylenebis(4-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), stearyl-β-(3,5-di-t-butyl-4-hydroxylphenol)propionate, tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, 1, Examples include 3,5-trimethyl-2,4,6-tris(3,5-di-t-4-hydroxybenzyl)benzene, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenol)butane, pentaerythristyltetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 1,1-bis(4-oxyphenyl)cyclohexane, dialkylphenol sulfide, alkylphenol condensate, and styrenated phenol. Among these, a hindered phenol antioxidant having one or two t-butyl groups on the aromatic ring adjacent to the carbon atom to which the phenolic hydroxy group is bonded is preferred, and pentaerythristyl tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] is more preferred.

[0023] Examples of amine antioxidants include N,N'-di-2-naphthyl-p-phenylenediamine, phenyl-α-naphthylamine, phenyl-β-naphthylamine, 4,4'-dimethoxydiphenylamine, N,N'-diphenyl-p-phenylenediamine, N-phenyl-N'-cyclohexyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, aldol-α-naphthylamine, 4,4'-diaminodiphenylmethane, acetaldehyde aniline, and reaction products of diphenylamine and acetone.

[0024] Phosphorus antioxidants include tris(isodecyl)phosphite, tris(tridecyl)phosphite, phenyl isooctyl phosphite, phenyl isodecyl phosphite, phenyl di(tridecyl)phosphite, diphenyl isooctyl phosphite, diphenyl isodecyl phosphite, diphenyl tridecyl phosphite, triphenyl phosphite, tris(nonylphenyl)phosphite, 4,4'-isopropylidenediphenol alkyl phosphite, trisnonylphenyl phosphite, tris(dinonylphenyl)phosphite, tris(2,4-di-t-butylphenyl)phosphite, tris(biphenyl)phosphite, distearyl pentaerythritol diphosphite, and di(2,4-di-t-butylphenyl)pentaerythritol. Examples of suitable phosphate phosphates include tetratridecyl 4,4'-butylidenebis(3-methyl-6-t-butylphenol)diphosphite, hexatridecyl 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butanetriphosphite, 3,5-di-t-butyl-4-hydroxybenzyl phosphite diethyl ester, sodium bis(4-t-butylphenyl)phosphite, sodium 2,2-methylene-bis(4,6-di-t-butylphenyl)phosphite, 1,3-bis(diphenoxyphosphonyloxy)benzene, and ethyl bis(2,4-ditert-butyl-6-methylphenyl)phosphite. Other suitable phosphate phosphate phosphates include oligomer and polymer compounds having a phosphite structure.

[0025] Examples of sulfur-based antioxidants include 2,2-thiodiethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,4-bis[(octylthio)methyl]-o-cresol, 2,4-bis[(laurylthio)methyl]-o-cresol, 2,2-bis{[3-(dodecylthio)-1-oxopropoxy]methyl}propane-1,3-diylbis[3-(dodecylthio)propionate], and 2,2-thiodiethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]. Other oligomeric and polymeric compounds having a thioether structure can also be used.

[0026] The antioxidant prevents deterioration of the hot melt adhesive during melting, and as a result, in filter applications, maintains moldability and the appearance quality of the filter after molding. The hot melt adhesive of the present disclosure preferably contains an antioxidant from the viewpoint of suppressing heat discoloration during melting and maintaining the design quality with minimal difference in hue of the hot melt adhesive applied to a white filter medium. These antioxidants may be used alone or in combination of two or more.

[0027] The content of the antioxidant in the hot melt adhesive of the present disclosure is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 4 parts by mass, and even more preferably 0.3 to 3 parts by mass, per 100 parts by mass of the hot melt adhesive.

[0028] In addition to the polyolefin and the antioxidant, the hot melt adhesive of the present disclosure may contain waxes such as crystalline polypropylene wax and crystalline polyethylene wax, tackifiers and other tackifiers, as well as other components such as fillers, ultraviolet absorbers, flow adjusters, deodorizers, antibacterial agents, adhesion improvers, and pigments.

[0029] (Waxes such as crystalline polypropylene wax and crystalline polyethylene wax) "Crystalline polypropylene wax" is a waxy crystalline polypropylene. The number average molecular weight is not particularly limited as long as it exhibits the intended performance of the present invention, but is preferably 2,000 to 20,000, more preferably 2,000 to 10,000, and even more preferably 2,000 to 7,000.The softening point is preferably 120 to 160°C, and more preferably 140 to 160°C.

[0030] "Crystalline polyethylene wax" is a waxy crystalline polyethylene. The number average molecular weight is not particularly limited as long as it exhibits the intended performance of the present invention, but is preferably 1,000 to 10,000, more preferably 1,000 to 4,000, and even more preferably 1,000 to 3,000. The specific gravity is preferably 0.90 to 1.00, more preferably 0.92 to 1.00, and even more preferably 0.95 to 1.00. The softening point is preferably 100 to 130°C, and more preferably 120 to 130°C.

[0031] Waxes such as crystalline polypropylene wax and crystalline polyethylene wax can be used in the hot melt adhesive of the present disclosure, and the amount of waxes to be added is preferably 5 to 30 mass %, more preferably 10 to 20 mass %, relative to the total mass of the hot melt adhesive.

[0032] (tackifiers and other adhesive components) The hot melt adhesive of the present disclosure may contain a tackifier (adhesive imparting agent) from the viewpoint of wettability to the filter medium. Examples of the tackifier include petroleum resins; rosin derivatives such as rosin ester, gum rosin, tall oil rosin, hydrogenated rosin ester, maleated rosin, and disproportionated rosin ester; terpene-based resins mainly composed of terpene phenol resins, α-pinene, β-pinene, limonene, and the like; coumarone-indene-based resins; hydrogenated aromatic copolymers; styrene-based resins; phenol-based resins; xylene-based resins; and (meth)acrylic polymers.

[0033] Among these, the tackifier preferably contains at least one compound selected from the group consisting of petroleum resins, rosin derivatives, and hydrogenated resins of terpene-based resins. These have a white hue, so there is no significant difference in hue from white filter media, and the design can be maintained.

[0034] From the viewpoints of thermal cycle durability, adhesion at room temperature, and ease of handling, the content of the tackifier is preferably from 1 to 70% by mass, more preferably from 10 to 65% by mass, even more preferably from 20 to 60% by mass, and especially preferably from 30 to 55% by mass, relative to the total mass of the hot melt adhesive.

[0035] (Other ingredients) Examples of fillers include fumed silica, surface-treated fumed silica, precipitated silica, diatomaceous earth, quartz powder, calcium carbonate, and carbon black. By including a filler, it is possible to improve the heat resistance, elastic modulus, blocking resistance, and the like. Examples of the ultraviolet absorber include benzophenone-based ultraviolet absorbers and benzotriazole-based ultraviolet absorbers such as 2-(2-hydroxy-5-methylphenyl)benzotriazole.

[0036] The other components may be used alone or in combination of two or more. The content of the other components is not particularly limited, but is preferably 5% by mass or less, and more preferably 1% by mass or less, relative to the total mass of the hot melt adhesive.

[0037] The hot melt adhesive of the present disclosure can be used in fields where hot melt adhesives are normally used, such as laminating cardboard, paper, wood or nonwoven fabrics, and assembling parts onto metal or plastic, but is particularly suitable for assembling filters in which filter media such as nonwoven fabric and / or paper are pleated and the processed filter media is then fixed to a frame. The hot melt adhesive of the present disclosure is suitable for applications in which pleated filter media are set in a frame, such as processing filters for air purifiers, humidifiers, vacuum cleaners, and salt damage prevention devices. Furthermore, the hot melt adhesive of the present disclosure has excellent adhesive durability in high-temperature environments, and therefore can be suitably used for air filters for automobile interiors.

[0038] An example of a method for assembling a filter using the hot melt adhesive of the present disclosure on a pleated filter medium and frame is given below. (1)Top adhesive When the filter material is pleated and the overall filter material is plate-shaped, hot melt adhesive is applied in lines or dots across the pleats, aiming at the tops of the pleats, and then allowed to harden. This prevents the pleats from moving and coming into contact with each other. The adhesive may be applied in a line or in dots near the tops of the pleats, aiming at the spaces between the tops of adjacent pleats. A hot melt applicator or a hot melt gun may be used for application. The plate-shaped filter thus obtained can also be curved and processed into a cylindrical shape or a part thereof (semi-cylindrical shape).

[0039] (2) End adhesion The pleated plate-shaped filter material is preferably fixed in a frame arranged around it to prevent fluid leakage when used as a filter and to prevent it from falling off during transportation or running. For this reason, it is preferable to bond the end of the pleats of the filter material to an end plate constituting the frame. Furthermore, it is also preferable to bond the end perpendicular to the pleats to an end plate constituting the frame. To achieve this, a narrow space is created between the end of the filter material and the end plate, and adhesive is injected to secure the filter material in place. It is preferable to use a hot melt adhesive and inject the adhesive from above, for example, as this shortens the process time.

[0040] The filter of the present disclosure is assembled by both the top and edge bonding processes, but the order of the top and edge bonding processes may be reversed if necessary. Alternatively, individual end plates and pleated filter media may be edge bonded first, and then the end plates may be assembled to form a frame. Furthermore, the frame may be a one-piece molded product shaped like a picture frame. In this case, the edge bonding is performed by bonding the pleated filter media to each surface constituting the inner surface of the frame, rather than the end plates. [Example]

[0041] EXAMPLES The present invention will be specifically and in detail explained below with reference to examples and comparative examples, but the present invention is not limited to these examples in any way.

[0042] (Hot melt adhesive preparation) Reference example 1 A 1.5-liter MS open-type kneader manufactured by Moriyama Corporation was set to 230°C, and 0.3 parts by mass of a phenolic antioxidant (antioxidant A), 0.3 parts by mass of a sulfur-based antioxidant (antioxidant B), and 15 parts by mass of crystalline polypropylene (resin A) were added and melt-mixed. Then, 50 parts by mass of amorphous polypropylene (resin B) and 35 parts by mass of amorphous polypropylene (resin D) were added in sequence and heated and mixed to obtain hot melt adhesive 1.

[0043] Reference examples 2~9 Hot melt adhesives 2 to 4 and 6 to 9 were prepared by changing the type and amount of resin, antioxidant, and type and amount of additives as shown in Table 1.

[0044] The resins, antioxidants and additives used in the above Reference Examples are as follows: (Resin A) Crystalline polypropylene: Number average molecular weight 10,000, glass transition temperature 14 The melt viscosity at 5°C and 190°C is 42,000 mPa·s. (Resin B) Amorphous polypropylene: Softening point is 152°C, and melt viscosity at 190°C is 1,500 mPa·s. (Resin C) Amorphous polypropylene: Softening point is 141°C, and melt viscosity at 190°C is 3,000 mPa·s. (Resin D) Amorphous polypropylene: Softening point is 124°C, and melt viscosity at 190°C is 2,700 mPa·s. (Resin E) Amorphous polypropylene: Softening point is 107°C, and melt viscosity at 190°C is 50,000 mPa·s. (Resin F) Crystalline polyethylene: Melting point 98°C, Melt flow index 145g / 10min (Temperature 190°C, Load 2.16kg) (Resin G) Ethylene vinyl acetate copolymer resin: 14% vinyl acetate, melting point 77°C, melt flow index 2,500g / 10min (temperature 190°C, load 2.16kg) (Resin H) Polyamide resin: Softening point is 135°C, and melt viscosity at 190°C is 4,800 mPa·s.

[0045] (Antioxidant A) Hindered phenol antioxidant (Antioxidant B) Sulfur-based antioxidant (Additive A) Tackifier (hydrogenated DCPD resin): softening point is 105℃ (Additive B) Polypropylene wax: softening point 152°C

[0046] [Table 1]

[0047] Examples 1 to 5, Comparative Examples 1 to 4 (Evaluation of the physical properties of hot melt adhesives) (A) Melt viscosity at 190°C measured according to ASTM D3236-73 using Spindle No. SC4-27: The Brookfield viscometer used was an RVT manufactured by Brookfield, Inc. The rotation speed was 2.5 rpm for Comparative Example 2 and 20 rpm for the others. (B) Softening point measured in accordance with JIS K6863-1994 using silicone oil as a heat medium: The temperature of the test room was 23±5°C and the relative humidity was 40-70%. (C) The temperature at which the test piece softens and the displacement in the shrinkage direction becomes 0.05 mm when a cylindrical detection rod with a diameter of 3 mm is applied to a test piece cut into a 5 mm square from a sample sheet formed to a thickness of 2 mm in accordance with JIS K7196-1991, nitrogen gas is flowed at a rate of 100 ml / min, a load of 10 gf is applied, and the temperature is raised at a rate of 5°C / min: Measurements were performed using a thermomechanical analyzer TMA-60 (Shimadzu Corporation). (D) In ​​accordance with JIS K6850-1999, a hot melt adhesive melted at 180°C is applied in the form of a 4 to 5 mm bead to a 10 mm x 25 mm adhesive area at one end of a 100 mm x 25 mm polypropylene plate, and within 5 seconds, one end of another polypropylene plate is placed over the adhesive area and pressed with a pressure of 24 kgf for 5 seconds to form a test piece. The test piece is left to stand at 25°C for 16 hours, and then the adhesive strength when both polypropylene plates of the test piece are pulled in opposite directions at 80°C at a rate of 50 mm / min is: The thickness of the applied adhesive was approximately 0.2 mm. Measurements were taken using an Autograph AGS-X (Shimadzu Corporation). (E) One end of the test piece is fixed vertically to a jig in a thermostatic chamber, a 500 g weight is attached to the other end, and the test piece is left standing at 38°C for 15 minutes. After that, the temperature is increased at a rate of 0.4°C / min. The temperature at which the bonded part can no longer withstand the load of the weight and the weight falls: Measurements were performed using a high-spec oven EH-602 (Kusumoto Chemical Co., Ltd.). The results of these physical property evaluations are shown in Table 2.

[0048] (Performance evaluation of hot melt adhesives and filters) (1) Heat stability test of hot melt adhesive An aluminum foil cup was placed in a 150cc metal container and 30g of hot melt adhesive was placed inside. The container was then placed in a hot air circulating thermostatic chamber adjusted to 190°C. After 24 hours, the sample was removed from the thermostatic chamber, the aluminum foil was removed, and the surface of the sample was poked with tweezers and the surface condition was visually observed. Those without skinning on the surface were rated A, and those with skinning were rated F. (2) Heat resistance test of the filter A sample filter medium was prepared by folding and pleating a nonwoven polypropylene fabric. A line of hot melt adhesive was applied to this sample filter medium in the direction perpendicular to the pleats (horizontal direction). As a result, a nearly uniform layer of hot melt adhesive was formed on the surface of the filter medium. Next, both end faces of the sample filter medium fixed with the hot melt adhesive in the direction in which the pleats extend were bonded to polypropylene end plates with the same hot melt adhesive as above to form a sample filter. The obtained sample filters with end plates were left to stand in a hot air circulating thermostatic chamber adjusted to 80°C for 72 hours, after which the adhesion state of the filter media edge and end plate of the filter was checked. Those without abnormalities were rated A, and those confirmed to have peeled were rated F. The performance evaluation results are shown in Table 2.

[0049] [Table 2]

[0050] As is clear from Examples 1 to 5, Examples 1 to 5 of the present invention satisfy the following three requirements: (A) a melt viscosity at 190°C measured in accordance with ASTM D3236-73 using Spindle No. SC4-27 of 1,000 mPa or more and 15,000 mPa or less; (B) a softening point measured in accordance with JIS K6863-1994 using silicone oil as a heat medium of 130°C or more and 170°C or less; and (C) a temperature of 90°C or more at which the test piece softens and shrinks to 0.05 mm when a 3 mm diameter cylindrical detection rod is attached to a 5 mm square test piece cut from a 2 mm thick sample sheet in accordance with JIS K7196-19·BR>X1, nitrogen gas is flowed at a rate of 100 ml / min, a load of 10 gf is applied, and the temperature is raised at a rate of 5°C / min. Thus, the heat resistance test of the filters of Examples 1 to 5 is satisfactory, and the heat stability is good.

[0051] Furthermore, as is clear from Examples 1 to 4, in accordance with (D) JIS K6850-1999, a hot melt adhesive melted at 180°C was applied in the form of a 4 to 5 mm bead to a 10 mm x 25 mm adhesive portion at one end of a 100 mm x 25 mm polypropylene plate, and within 5 seconds, one end of another polypropylene plate was placed over the adhesive portion and pressed with a pressure of 24 kgf for 5 seconds to form a test piece. The test piece was left to stand at 25°C for 16 hours, and then the adhesive strength when both polypropylene plates of the test piece were pulled in opposite directions at 80°C at a rate of 50 mm / min was 15 N / cm. 2 In addition to the above, Examples 1 to 4 also satisfied the two requirements that when one end of the test piece was fixed vertically to a jig in a constant temperature bath, a 500 g weight was attached to the other end, and the test piece was left standing at 38°C for 15 minutes, and then the temperature was raised at a rate of 0.4°C / min, the adhesive part could no longer withstand the load of the weight and the temperature at which the weight dropped was 90°C or higher. These examples also performed well in the heat stability test, proving that deterioration of hot melt adhesives can be prevented in high-temperature environments.

[0052] In contrast, Comparative Examples 1 to 4, which do not satisfy the above requirements (A) to (C), showed poor results in the heat resistance test of the filters, and it was found that the filters are not suitable for use in high-temperature environments, such as being loaded into automobiles.

Claims

1. (A) The melt viscosity at 190°C measured in accordance with ASTM D3236-73 using Spindle No. SC4-27 is 1,000 mPa s or more and 15,000 mPa s or less; (B) The softening point measured in accordance with JIS K6863-1994 using silicone oil as a heat medium is 130°C or higher and 170°C or lower, (C) In accordance with JIS K7196-1991, a cylindrical detection rod having a diameter of 3 mm is placed on a test piece cut into a 5 mm square from a sample sheet molded to a thickness of 2 mm, nitrogen gas is flowed at a rate of 100 ml / min, a load of 10 gf is applied, and the temperature is raised at a rate of 5°C / min. When the test piece softens and the displacement in the shrinkage direction becomes 0.05 mm, the temperature is 90°C or higher. including amorphous polyolefins and crystalline polyolefins, A hot melt adhesive, characterized in that the amorphous polyolefin and the crystalline polyolefin are polypropylene.

2. (D) In ​​accordance with JIS K6850-1999, a hot melt adhesive melted at 180°C is applied in the form of a 4 to 5 mm bead to a 10 mm x 25 mm adhesive portion at one end of a 100 mm x 25 mm polypropylene plate, and within 5 seconds, one end of another polypropylene plate is placed over the adhesive portion and pressed with a pressure of 24 kgf for 5 seconds to form a test piece. The test piece is left to stand at 25°C for 16 hours, and then both polypropylene plates of the test piece are pulled in opposite directions at 80°C at a rate of 50 mm / min, and the adhesive strength is 15 N / cm2 or more, (E) One end of the test piece is fixed vertically to a jig in a thermostatic chamber, a 500 g weight is attached to the other end, and the test piece is left standing at 38°C for 15 minutes. After that, the temperature is raised at a rate of 0.4°C / min. When the adhesive part can no longer withstand the load of the weight and the weight falls, the temperature is 90°C or higher.

2. The hot melt adhesive of claim 1.

3. The hot melt adhesive according to claim 1 or 2, wherein the content of the amorphous polyolefin and the crystalline polyolefin is 70 to 99 mass%.

4. The hot melt adhesive according to any one of claims 1 to 3, wherein the crystalline polyolefin has a number average molecular weight of 2,000 to 30,000.

5. The hot melt adhesive according to any one of claims 1 to 4, which is used in assembling a filter composed of a pleated filter medium and a frame surrounding the filter medium, to prevent the pleats from contacting each other by being placed between adjacent pleats, and / or to bond the filter medium to the frame.

6. 6. The hot melt adhesive according to claim 5, wherein the filter medium is a polypropylene nonwoven fabric.

7. 7. The hot melt adhesive according to claim 5, wherein the filter is an air filter for use in an automobile cabin.

8. A filter having a pleated filter medium and a frame surrounding the filter medium as constituent parts, assembled using the hot melt adhesive according to any one of claims 1 to 6.

9. 8. An air filter for use in an automobile cabin, comprising pleated filter material and a frame surrounding the filter material as components, assembled using the hot melt adhesive according to any one of claims 1 to 7.

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