JP7064822B2 - Hot melt adhesive and hot melt adhesive sheet - Google Patents

Description

The present invention relates to a hot melt adhesive and a hot melt adhesive sheet, and more particularly to a hot melt adhesive sheet provided with an adhesive layer composed of a hot melt adhesive containing a styrene-based copolymer and a hot melt adhesive.

Conventionally, in applications such as bonding members to each other, a hot melt adhesive sheet having a laminated structure in which an adhesive layer made of a hot melt adhesive is formed on one side or both sides of a base material layer made of a non-woven fabric or the like, or a hot melt adhesive. An adhesive layer consisting of a single layer Hot melt adhesive sheet is used.
As the hot melt adhesive, for example, as shown in Patent Document 1 below, a type containing a styrene-based block copolymer is known.

By the way, the hot melt adhesive sheet has conventionally been used for adhering a housing and a lid of a small electronic device.
Adhesive sheets in this type of application are required to exhibit not only a function as an adhesive but also a function as a sealing material for preventing the inflow of water or water vapor into the device.
The hot-melt adhesive sheet used for this type of application is, for example, when a small electronic device is used in a hot and humid environment, the hot-melt adhesive constituting the adhesive layer adheres under the influence of water vapor. It is easy to reduce the sex.
For this reason, it is required that the adhesiveness of the hot melt adhesive sheet is not easily affected by humidity and that the adhesiveness is not easily lowered even when exposed to a high humidity atmosphere.

Japanese Unexamined Patent Publication No. 2014-043520

As described above, the hot melt adhesive constituting the adhesive layer of the hot melt adhesive sheet is required to have excellent moisture resistance.
It should be noted that excellent moisture resistance is not required only in a specific application such as when it is used for a hot melt adhesive sheet which is expected to function as a sealing material.
That is, excellent moisture resistance is one of the characteristics widely and commonly required for hot melt adhesives used in various applications.
However, in the conventional hot melt adhesive, one having excellent moisture resistance has not been found, and there is a problem that it is difficult to satisfy the above-mentioned requirements.
INDUSTRIAL APPLICABILITY The present invention has been made to solve such a problem, and provides a hot melt adhesive having moisture resistance, and by extension, a hot melt adhesive sheet whose adhesiveness is not easily deteriorated even when exposed to a high humidity atmosphere. The challenge is to provide it.

As a result of diligent studies to solve the above problems, the present inventor has found that the hot melt adhesive can exhibit excellent moisture resistance by forming the hot melt adhesive with a specific component. It led to the completion of the invention.

That is, the present invention relating to a hot melt adhesive for solving the above-mentioned problems is a hot melt adhesive containing a styrene-based block copolymer, which is an epoxy resin, a curing agent for curing the epoxy resin, and a curing agent. The content of the epoxy resin with respect to 100 parts by mass of the styrene-based block copolymer is 20 parts by mass or more and 100 parts by mass or less, and the curing agent is a phenol-based curing agent to accelerate the curing. The agent is 1-cyanoethyl-2-ethyl-4-methylimidazole.

Further, the present invention relating to an adhesive hot melt sheet for solving the above problems is a hot melt adhesive sheet provided with an adhesive layer made of a hot melt adhesive, and the hot melt adhesive is a styrene block. The content of the epoxy resin is 20 parts by mass or more and 100 parts by mass with respect to 100 parts by mass of the styrene-based block copolymer, which contains a polymer, an epoxy resin, a curing agent for curing the epoxy resin, and a curing accelerator. The curing agent is a phenol resin-based curing agent, and the curing accelerator is 1-cyanoethyl-2-ethyl-4-methylimidazole.

According to the present invention, a hot melt adhesive having excellent moisture resistance can be provided, and a hot melt adhesive sheet that does not easily deteriorate adhesiveness even when exposed to a high humidity atmosphere can be provided.

The schematic plan view which shows the hot melt adhesive sheet of one Embodiment. FIG. 1 is a schematic cross-sectional view showing a cross-sectional view taken along the line AA'in FIG. The figure which showed the aspect which uses the hot melt adhesive sheet as a sealing material. The schematic cross-sectional view which showed the state of the cross section of the hot melt adhesive sheet of another embodiment.

Hereinafter, a preferred embodiment of the present invention will be described by exemplifying a case where the hot melt adhesive sheet is used as an annular sealing material.
FIG. 1 shows a sealing material 1 formed of the hot melt adhesive sheet of the present embodiment, and shows a sealing material 1 formed by punching so that the shape in a plan view is a rectangular frame shape. be.
The sealing material 1 has a single-layer structure as shown in FIG. 2 for its cross-sectional structure.
That is, the hot melt adhesive sheet of the present embodiment has a single layer structure of only the adhesive layer 10 formed by the hot melt adhesive.

The hot melt adhesive constituting the adhesive layer 10 contains a styrene-based block copolymer, an epoxy resin, and a curing agent for curing the epoxy resin, with respect to 100 parts by mass of the styrene-based block copolymer. The content of the epoxy resin is 20 parts by mass or more and 100 parts by mass or less, and the curing agent is a phenol-based curing agent.

Examples of the styrene-based block copolymer contained in the hot melt adhesive include a styrene-butadiene copolymer (SBS), a styrene-isoprene copolymer (SIS), and styrene which is a hydrogenated additive thereof. Examples thereof include an ethylene-butylene-styrene copolymer (SEBS) and a styrene-ethylene-propylene-styrene copolymer (SEPS).

Examples of the epoxy resin contained in the hot melt adhesive include bisphenol A type epoxy resin, bisphenol F type epoxy resin, cresol novolac type epoxy resin, alicyclic epoxy resin, and phenol novolac type epoxy resin.

The phenol-based curing agent contained in the hot melt adhesive is not particularly limited as long as it acts as a curing agent for the epoxy resin, and the phenol-based curing agent is, for example, phenol novolac. Examples thereof include novolak-type phenol resins such as resins, phenol-aralkyl resins, cresol novolak resins, tert-butylphenol novolak resins, and nonylphenol novolak resins, resol-type phenol resins, and polyoxystyrenes such as polyparaoxystyrene.

The styrene-based block copolymer, the epoxy resin, and the phenol-based curing agent do not need to be contained alone in the hot-melt adhesive, and even if two or more of them are contained in the hot-melt adhesive. good.

The hot-melt adhesive contains the styrene-based block copolymer mainly as a base polymer for exhibiting tackiness and toughness in the hot-melt adhesive, and the epoxy resin mainly exhibits excellent adhesiveness. It is contained as an ingredient for.
The hot melt adhesive has a ratio of P ₁ and P ₂ when the content of the styrene-based block copolymer is P ₁ (% by mass) and the content of the epoxy resin is P ₂ (% by mass). It is important that P ₁ : P ₂ ) is 100: 20 to 100: 100.
The ratio (P ₁ : P ₂ ) is preferably 100: 25 to 100: 80, preferably 100: 30 to 100: 80, in order to remarkably exhibit excellent adhesiveness and moisture resistance of the hot melt adhesive. It is more preferably 60, and particularly preferably 100:40 to 100:50.

Here, the content of the styrene block copolymer and the epoxy resin is the ratio of the total amount to the total amount of the hot melt adhesive when a plurality of types of these are contained in the hot melt adhesive. means.

The hot melt adhesive is preferably a styrene-ethylene-butylene-styrene copolymer (SEBS) in part or in whole of the styrene-based block polymer, and 50% by mass or more of the styrene-based block copolymer is used. It is more preferable that it is a styrene-ethylene-butylene-styrene copolymer (SEBS), and it is further that 80% by mass or more of the styrene-based block copolymer is a styrene-ethylene-butylene-styrene copolymer (SEBS). It is particularly preferable that 90% by mass or more of the styrene-based block copolymer is a styrene-ethylene-butylene-styrene copolymer (SEBS).

Among them, the styrene-ethylene-butylene-styrene copolymer (SEBS) contained in the hot melt adhesive preferably has a styrene content of 20% by mass to 50% by mass.
When a plurality of types of styrene-ethylene-butylene-styrene copolymer (SEBS) are contained in the hot melt adhesive, the average value (weighted average) of the styrene content is 20% by mass or more. It is preferable to adjust the content to 50% by mass.

In the present embodiment, it is preferable that the thickness of the adhesive layer 10 is secured to some extent when the sealing material 1 (hot melt adhesive sheet) is heat-bonded. Therefore, the styrene-based block copolymer is in a heated state. Those that do not show excessive fluidity are preferable.
On the other hand, when the sealing material is heat-bonded, it is preferable that the sealing material exhibits a certain degree of tackiness. Therefore, the styrene-based block copolymer softens to some extent in a heated state and exhibits fluidity. Is preferable.

In order to satisfy such conflicting requirements, the hot melt adhesive uses a styrene-based block copolymer that exhibits fluidity when heated and a styrene-based block that has lower fluidity than the styrene-based block copolymer. It is preferable to contain two or more types of styrene-based block copolymers with the copolymer.

Among these two or more types of styrene-based block copolymers, the styrene-based block copolymer (hereinafter, also referred to as “highly fluid component”) that exhibits relatively high fluidity when heated is the method A of ISO1133. The melt flow rate (hereinafter, also simply referred to as “MFR”) measured under the conditions of 230 ° C. and 5 kgf is preferably 3 g / 10 min to 8 g / 10 min.
Further, a styrene-based block copolymer (hereinafter, also referred to as "low-fluidity component") having a relatively low fluidity at the time of heating as compared with this styrene-based block copolymer (high-fluidity component) has an MFR. It is preferably less than 3 g / 10 min.

Further, the hot melt adhesive is a styrene-based block having a melt flow rate (MFR) value of 1.5 g / 10 min or less (0 g / 10 min to 1.5 g / 10 min) as a part or all of the low fluidity component. It is preferable to contain a copolymer (hereinafter, also referred to as "ultra-low fluidity component").
The hot melt adhesive contains the low fluidity component in a larger amount than the high fluidity component in order to surely prevent the thickness of the adhesive layer 10 from being excessively reduced at the time of thermal adhesion. It is preferable to be.

Further, the low fluidity component preferably has 50% by mass or more of the ultra-low fluidity component, more preferably 80% by mass or more of the ultra-low fluidity component, and 90% by mass or more of the ultra-low fluidity component. It is particularly preferable that it is an ultra-low fluid component.
When the content of the low fluidity component in the hot melt adhesive is P _1L (mass%) and the content of the high fluidity component is P _1H (mass%), the low fluidity component and the high fluidity component The ratio (P _1L : P _1H ) is preferably 6: 4 to 9: 1, and more preferably 65: 35 to 80:20.

The epoxy resin contained in the hot melt adhesive is preferably a novolak type rather than a bisphenol type in that the epoxy group is abundant and excellent adhesiveness is easily exhibited in the hot melt adhesive, and cresol novolak is preferable. Molded ones are preferred.
Among them, the epoxy resin contained in the hot melt adhesive is preferably an o-cresol novolak type epoxy resin containing o-cresol as a main starting material in part or in whole.
In the hot melt adhesive, 50% by mass or more of the epoxy resin contained is preferably an o-cresol novolak type epoxy resin, and 80% by mass or more is particularly preferably an o-cresol novolac type epoxy resin. It is particularly preferable that the mass% or more is o-cresol novolak type epoxy resin.

The phenolic curing agent contained in the hot melt adhesive is preferably a phenol aralkyl resin.
The phenolic curing agent is preferably contained in the hot melt adhesive so that the number of phenolic hydroxyl groups ( _{NOH) is a predetermined ratio with respect to the number of epoxy groups (Nepx )} of the epoxy resin. ..
More specifically, the ratio ( _NOH : _Nepx ) between the number of phenolic hydroxyl groups ( _{NOH) and the number of epoxy groups (Nepx )} in the hot melt adhesive is 1: 1.5 to 1.5. It is preferably in the range of 1, and preferably in the range of 1: 1.2 to 1.2: 1.

The hot melt adhesive contains a curing accelerator for accelerating the curing reaction of the epoxy resin by the phenolic curing agent.
Examples of the curing accelerator include imidazoles.
Examples of the imidazoles contained in the hot melt adhesive include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole and 2-. Phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methyl Imidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 2,4-diamino-6- (2-methylimidazolylethyl) -1,3,5-triazine, 2,4-diamino -6- (2-Undecylimidazolylethyl) -1,3,5-triazine, 2,4-diamino-6- (2-ethyl-4-methylimidazolylethyl) -1,3,5-triazine, 2- Examples thereof include phenyl-4,5-dihydroxymethylimidazole and 2-phenyl-4-methyl-5-hydroxymethylimidazole.

Among them, imidazoles, which are essential components of hot melt adhesives, are 1-cyanoethyl-2-ethyl-4-methylimidazole.
The imidazoles contained in the hot melt adhesive have a value obtained by adding the number of active hydrogens ( _NH ) to the number of phenolic hydroxyl groups ( _{NOH) with respect to the number of epoxy groups (Nepx )} . It is preferably contained so as to be quantitative.
More specifically, the ratio of the number of epoxy groups ( _Nepx ) to the total number of active hydrogens ( _NH ) and the number of phenolic _hydroxyl groups (NOH) in the hot melt adhesive ( _NOH : [ _NH ]. + N _epx ]) is preferably 1: 1.5 to 1.5: 1, preferably 1: 1.2 to 1.2: 1.

In addition to the above, the hot melt adhesive may contain a tackifier or the like.
Examples of the tackifier include rosin-terpene-based ones and petroleum resin-based ones. In the former case, hydrogenated terpenes and the like are preferable, and in the latter case, hydrogenated petroleum resin (alicyclic saturated hydrocarbon). ) And polyalphamethylstyrene are preferable.
When these tackifiers are contained in a hot melt adhesive, the total amount thereof is preferably 50 parts by mass to 150 parts by mass with respect to 100 parts by mass of the styrene-based block copolymer. ..

The hot melt adhesive of the present embodiment may further contain general plastic compounding agents such as an antioxidant, an antioxidant, a flame retardant, a filler, and a colorant.

For the hot melt adhesive sheet, for example, a varnish is prepared with an organic solvent capable of dissolving the styrene block copolymer or epoxy resin and a hot melt adhesive, and the varnish is applied to a separator film that has been surface-peeled. Then, a wet coating film is formed, and the wet coating film is passed through a drying device such as a hot air circulation oven together with a separator film to be dried.

Further, the hot melt adhesive sheet is, for example, two sheets obtained by melting and kneading the hot melt adhesive with an extruder equipped with a flat die, extruding the extruded sheet into a sheet shape from the flat die, and surface-peeling the extruded sheet. The hot melt adhesive can be cooled and solidified by being sandwiched between the separator films of the above and passed between a pair of cooling rollers, and the sheet thickness can be adjusted by the cooling rollers.

In the hot melt adhesive sheet, it is preferable that the epoxy resin has reactivity until it is used for adhering members.
Therefore, the hot-melt adhesive sheet of the present embodiment is exemplified above 2 in that it can prevent the hot-melt adhesive from becoming too hot and excessively advancing the curing reaction of the epoxy resin at the time of its production. It is preferably produced by the former method of the two methods.

Here, it can be confirmed that the curing reaction of the epoxy resin contained in the hot melt adhesive sheet has not proceeded excessively because the epoxy group remains without opening the ring, and the epoxy group opens. It can be confirmed by using a Fourier transform infrared spectrophotometer (FTIR) that it remains without being left.
Specifically, the fact that the epoxy group remains without opening the ring is confirmed by the fact that when the hot melt adhesive is measured by FTIR, a peak indicating the presence of the epoxy group appears at 925 to 899 cm ^-1 . can do.
If it is necessary to confirm whether the peak appearing at 925 to 899 cm ^-1 is due to an epoxy group, the resin composition may be heated above the softening point of the epoxy resin and then measured again by FTIR. It can be confirmed that the peak is due to the epoxy group by the corresponding change between the peak height and the peak height due to the hydroxyl group appearing at 3650 to 3140 cm ^-1 .

After obtaining a hot melt adhesive sheet with the hot melt adhesive in this way, the adhesive sheet is punched together with the separator film or the like by a Thomson blade mold or a punching press, and processed into a desired outer shape as shown in FIG. It can be a sealing material 1 having a rectangular frame shape.

Among the methods for producing a hot melt adhesive sheet, in the former method for preparing a varnish once, one side and the other side of the hot melt adhesive sheet are selected depending on the type of organic solvent used, the type of separator film, drying conditions, and the like. It is possible to easily impart different properties to and.
For example, the styrene-based block copolymer and the epoxy resin do not show good compatibility, and a microlayer separation structure (sea-island structure) between the matrix phase and the domain phase is shown by simply performing melt kneading or the like. As the organic solvent for selecting the above-mentioned materials and dissolving them to form a varnish, the first organic solvent having higher solubility in the epoxy resin than the styrene-based block copolymer and the above-mentioned organic solvent as compared with the epoxy resin. By adopting a mixed solvent with a second organic solvent having high solubility in the styrene-based block copolymer, a resin solution containing a large amount of the styrene-based block copolymer in the process of drying the wet coating film can be used. It is possible to form a state in which the resin solution containing a large amount of the epoxy resin repels each other.
Then, by drying the wet coating film, for example, a hot melt adhesive sheet having a higher epoxy resin concentration on the other side than on the one side in contact with the separator can be produced.

At this time, by adopting a separator film having a higher affinity for the styrene block copolymer than the epoxy resin, a hot melt adhesive sheet having a higher epoxy resin concentration on the other side than on the one side can be obtained. You can definitely get it.

Furthermore, when a high-density component such as an inorganic filler is contained in the varnish, the varnish has a low viscosity, so that the high-density component can be easily unevenly distributed by the action of gravity.
For example, when the separator film is horizontally conveyed so that the wet coating film is on the upper surface side and passed through the drying device, the high specific density component is settled, and the one-sided side in contact with the separator is higher than the other-sided side. A hot melt adhesive sheet having a high concentration of specific gravity components can be produced.

The hot-melt adhesive sheet having different concentrations of the components on the one-sided side and the other-sided side in this way is useful for applications in which different functions are required on each side.
For example, a hot-melt adhesive sheet in which the concentration of the epoxy resin differs between the one-sided side and the other-side side as described above is usually high in polarity because the epoxy resin has a higher polarity than a styrene-based block copolymer or the like. It can be said that it is suitable for adhering a member formed of a polymer and a member formed of a member having a low polarity.
Further, since the epoxy resin usually exhibits superior adhesiveness to the hot melt adhesive sheet as compared with the styrene-based block copolymer, for example, the hot melt adhesive sheet is interposed between two members to bond the members to each other. If it is used for this purpose, it can be used so as to bond the side having a high concentration of epoxy resin to the side where higher adhesiveness is required.

Even when the hot-melt adhesive sheet exhibits different characteristics on one side and the other side as described above, the styrene-based block is used together with the styrene-based block in order to exhibit excellent moisture resistance on both sides. It is preferable that the content of the epoxy resin with respect to 100 parts by mass of the polymer is 20 parts by mass or more and 100 parts by mass or less on both surfaces.

The thickness of the adhesive layer 10 of the hot melt adhesive sheet is not particularly limited, but when it is usually used as a sealing material, its thickness is about 10 μm to 1 mm. Will be done.
The hot melt adhesive exhibits good adhesiveness to a wide range of materials regardless of the mating material, and is unlikely to cause a decrease in adhesive strength due to hydrolysis or the like even in a high humidity environment.
Therefore, the sealing material 1 is suitable for forming equipment used in a high temperature and high humidity environment in that its characteristics can be effectively utilized.

When used as such a sealing material, the sealing material 1 of the present embodiment is usually one side of both surfaces of the adhesive layer 10 (hereinafter, also referred to as "first surface 10a") and others. It is used in such a form that the surface side (hereinafter, also referred to as “second surface 10b”) is adhered to different members.
In addition, FIG. 3 shows a state in which the sealing material 1 is interposed between two sheet-shaped members whose shape in a plan view is a rectangle corresponding to the shape defined by the outer contour line of the sealing material 1. It is a figure which showed an example of the use state as the sealing material 1 of the hot melt adhesive sheet which concerns on this embodiment.

As shown in this figure, when the hot melt adhesive sheet of the present embodiment is used as the sealing material 1, for example, the member is interposed between the two members in order to bond the two members. The first surface 10a is adhered to the first member (hereinafter, also referred to as "first sheet A1"), and the second surface 10b is attached to the second member (hereinafter, also referred to as "second sheet A2"). Used by adhering.
Further, the sealing material 1 is adhered to each of the first sheet A1 and the second sheet A2 so that the first sheet A1 and the second sheet A2 face each other with a slight distance between them. Can be used in.
That is, the rectangular frame-shaped sealing material 1 is used to isolate the space S inside the sealing material 1 and sandwiched between the first sheet A1 and the second sheet A2 from the external space.

When a small electronic device provided with such a sealed space S is used in a hot and humid environment such as outdoors in a tropical area or in a workplace of a food factory, the sealing material 1 and the first sheet A1 or the second sheet A2 are used. The adhesive interface tends to be an intrusion route for water vapor.
However, in the hot melt adhesive sheet of the present embodiment, the hot melt adhesive constituting the adhesive layer 10 exhibits excellent adhesiveness and is unlikely to cause a decrease in adhesive strength due to water vapor.
Therefore, the hot melt adhesive sheet of the present embodiment can exhibit excellent sealing properties for a long period of time by being used as a sealing material.

Since the sealing material 1 of the present embodiment can easily have different properties between the first surface 10a and the second surface 10b as described above, for example, the first sheet A1 and the second sheet A2 However, the surface to be adhered to the first surface 10a and the second surface 10b is formed of the resin composition, and the first resin composition and the second sheet forming the surface of the first sheet A1, respectively. It can be suitably used in a case where the second resin composition forming the surface of A2 has a different polarity.

Of the first resin composition and the second resin composition, on the lower polar side, for example, a low polar resin such as a polyethylene resin, a polypropylene resin, a polyphenylene ether resin, a polystyrene resin, or a polytetrafluoroethylene resin is used. Examples include those containing the main component.
As for the highly polar side, polyester resins such as polyethylene terephthalate resin, polyamide resins, acrylic resins such as polymethyl methacrylate, and high polar resins such as perfluorosulfonic acid resin are used as main components.

The sealing material 1 of the present embodiment exhibits good adhesiveness in addition to resin members such as metal members.
The use of the hot melt adhesive or the hot melt adhesive sheet in the present embodiment is not limited to the above-exemplified sealing material.
Further, in the above, the hot melt adhesive sheet having a single layer of the adhesive layer is exemplified, but the hot melt adhesive sheet of the present invention may be a laminated sheet and has a layer other than the adhesive layer. You may be doing it.
As a modification of the above-exemplified single-layer structure, the hot-melt adhesive sheet of the present invention has a three-layer structure as shown in FIGS. 4 (a) and 4 (b).

Explaining the hot melt adhesive sheet having a three-layer structure, the hot melt adhesive sheet 1'exemplified in FIG. 4 (a) has a base material layer 20 and an adhesive layer 10x laminated on both sides of the base material layer 20. , 10y and.

The base material layer 20 can be formed of, for example, a resin film or a fiber sheet, and the resin film is a film or hot melt made of a non-crystalline resin having a softening point equal to or higher than the softening temperature of the hot melt adhesive. Examples thereof include a film made of a crystalline resin having a melting point equal to or higher than the softening temperature of the adhesive.
Examples of the resin film include a polyethylene terephthalate resin film and the like.
The resin film may have improved adhesiveness to the adhesive layers 10x and 10y by mechanical surface treatment such as matte treatment and hairline treatment, and surface treatment by plasma treatment, primer treatment and the like.

In addition, examples of the fiber sheet include non-woven fabrics and woven fabrics made of organic fibers and inorganic fibers.
When a non-woven fabric is used as the fiber sheet, the non-woven fabric is a dry method such as a carding method or an air-laid method, a wet method, a spun bond method, a thermal bond method, a chemical bond method, a needle punch method, or a spun lace method (water flow). It may be formed by any method such as entanglement method) and stitch bond method.
When a woven fabric is used as the fiber sheet, the woven fabric may be formed by any method such as plain weave, twill weave, and satin weave.

Examples of the organic fiber, which is a material for forming the fiber sheet, include synthetic resin fibers, semi-synthetic fibers, regenerated fibers, and natural organic fibers.
Examples of the synthetic resin fiber include polyolefin resins such as polyethylene resin, polypropylene resin and cycloolefin polymer; polyester resins such as polyethylene terephthalate resin and polyethylene naphthalate resin; polyamide resins such as aliphatic polyamide resin and aromatic polyamide resin; Examples thereof include a polyether sulfide resin; a polyphenylene sulfide resin; a polyether ether ketone resin; a polyimide resin; and a fluororesin.
Examples of the regenerated fiber include rayon and acetate.
Examples of the natural organic fiber include pulp, cotton, hemp, silk and the like.
Examples of the inorganic fiber include rock wool, glass wool, carbon fiber, boron fiber, alumina fiber, metal fiber and the like.
These fibers do not need to be used alone for forming the fiber sheet, and a plurality of these fibers may be used in combination for forming the fiber sheet.
Further, the fiber may be used for forming the fiber sheet in the state of monofilament, or may be used for forming the fiber sheet in the state of multifilament.

By having the base material layer 20, such a hot melt adhesive sheet 1'can impart an appropriate elasticity to the hot melt adhesive sheet 1'and can be used for adhesion of the hot melt adhesive sheet 1'. However, it has an advantage that a significant decrease in thickness is unlikely to occur even when a pressure is applied in the thickness direction in a heated state.

Further, the hot melt adhesive sheet 1 "exemplified in FIG. 4 (b) is provided with porous sheets 30x and 30y on both sides of the adhesive layer 10.
The porous sheets 30x and 30y are formed of a material having a lower surface tackiness than the adhesive layer 10, and foreign matter adheres to the hot melt adhesive sheet 1 "before use of the hot melt adhesive sheet 1". It exerts the function of suppressing.
Further, the porous sheets 30x and 30y are provided so as to be able to impart excellent surface slipperiness to the hot melt adhesive sheet 1 ".
Further, the porous sheets 30x and 30y have a plurality of through holes (not shown), and when the hot melt adhesive sheet 1 ”is used for bonding, the hot melt adhesive that has been heated and softened is used. Since it is exuded to the surface through the through hole, it does not hinder the bonding work at all.
Therefore, the hot melt adhesive sheet 1 "exemplified in FIG. 4 (b) is suitable for adopting a hot melt adhesive having relatively high tackiness and high fluidity at the time of heating. It can be said that it is a thing.

Further, the hot melt adhesive sheet according to the present invention can be modified in various ways in addition to the above-mentioned modifications.
That is, the hot melt adhesive sheet according to the present invention is not limited to the above examples.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

(Hot melt adhesive)
In order to prepare a hot melt adhesive, three types of SEBS (styrene content is about 30%) having different molecular weights were prepared as styrene-based block copolymers.
The ones shown by the abbreviation of "SEBS1" in Table 1 below are those having a high molecular weight (ultra-low fluidity component) in which almost no flow is observed when MFR is measured.
Further, what is shown by the abbreviation of "SEBS2" in Table 1 below is a low molecular weight one (high fluidity component) showing an MFR of about 5 g / 10 min.
Further, those shown by the abbreviation of "SEBS3" in Table 1 below are those having an intermediate molecular weight between "SEBS1" and "SEBS2" and having an MFR of 1 g / 10 min or less (ultra-low fluidity component). be.
Two types of epoxy resins and three types of tackifiers were prepared for blending with this styrene-based block copolymer.
In Table 1 below, the abbreviation of "EPX1" is a bisphenol A type epoxy resin having a molecular weight of about 3800, and the one shown by the abbreviation of "EPX2" is an o-cresol novolak type epoxy resin.
In Table 1, the abbreviation of "TF1" is hydrogenated petroleum resin (alicyclic saturated hydrocarbon), the abbreviation of "TF2" is hydrogenated terpene resin, and the abbreviation of "TF3" is shown. Is a poly-α-methylstyrene resin.
In Table 1, the abbreviation of "HDN1" is a phenol-based curing agent (phenol aralkyl resin), and the abbreviation of "ACC1" is an imidazole-based curing accelerator (1-cyanoethyl-2-ethyl-). 4-Methylimidazole).

(evaluation)
A hot melt adhesive sheet (adhesive layer single layer) having a thickness of about 20 μm was prepared by the formulation shown in Table 1 above.
Next, a film having a thickness of about 200 μm made of a mixed resin (PPE / PS = 50/50) of a modified polyphenylene ether resin (m-PPE) and a polystyrene resin (PS) and a fluorine-based resin film having a thickness of about 50 μm were prepared. bottom.
Then, the hot melt adhesive sheet was sandwiched between these resin films, and these films were bonded to each other with the hot melt adhesive sheet under the bonding conditions of 130 ° C. for 30 seconds to prepare a laminated sheet.
A strip-shaped sample having a width of 10 mm and a length of 100 mm is cut out from this laminated sheet, and the strip-shaped sample is left in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH for 24 hours, and then 10 mm / min using a tensile tester. A 180 degree peel test was carried out at the tensile speed of the strip-shaped sample, and the initial peel strength of the strip-shaped sample was measured.
In the 180 degree peel test, the average value of the tensile stress in the peeling section of 3 mm to 18 mm after the start of the test was calculated, and this was used as the peel strength of the sample.
Further, the 180 degree peel test was carried out at n = 3 to calculate the arithmetic mean value, and the adhesiveness of the hot melt adhesive sheet was evaluated by this arithmetic mean value.
Then, after immersing the strip-shaped sample in hot water at 80 ° C. for a predetermined time (24h, 250h, 500h), a 180-degree peel test was carried out in the same manner as the initial peel strength, and the peel strength after the hot water immersion test was measured. ..
Table 2 below shows the measurement results (arithmetic mean value) of the initial peel strength and the peel strength after the hot water immersion test.
The results of calculating the ratio of the peel strength (adhesive strength retention rate) after the hot water immersion test to the initial peel strength are also shown in Table 2 below.

From the above, it can be seen that according to the present invention, a hot melt adhesive having excellent moisture resistance is provided, and a hot melt adhesive sheet whose adhesiveness does not easily deteriorate even when exposed to a high humidity atmosphere is provided. ..

1 Sealing material (hot melt adhesive sheet)
10 Adhesive layer 20 Base material layer

Claims (4)

A hot melt adhesive containing a styrene-based block copolymer.
All of the styrene-based block copolymers are styrene-ethylene-butylene-styrene copolymers (SEBS).
The epoxy resin further contains an epoxy resin, a curing agent for curing the epoxy resin, and a curing accelerator, and the content of the epoxy resin with respect to 100 parts by mass of the styrene-based block copolymer is 20 parts by mass or more and 100 parts by mass or less. A hot melt adhesive in which the curing agent is a phenolic curing agent and the curing accelerator is 1-cyanoethyl-2-ethyl-4-methylimidazole. As the styrene-based block copolymer, the first styrene-based block copolymer having a melt flow rate value of less than 3 g / 10 min measured under the condition of 230 ° C. and 5 kfg based on the method A of ISO1133, and the melt flow. A second styrene-based block copolymer having a late value of 3 g / 10 min or more and 8 g / 10 min or less is included, and the first styrene-based block is more than the second styrene-based block copolymer. The hot melt adhesive according to claim 1 , which contains a larger amount of polymer. A hot melt adhesive sheet having an adhesive layer made of a hot melt adhesive.
The hot melt adhesive contains a styrene-based block copolymer, an epoxy resin, a curing agent for curing the epoxy resin, and a curing accelerator.
All of the styrene-based block copolymers are styrene-ethylene-butylene-styrene copolymers (SEBS).
The content of the epoxy resin with respect to 100 parts by mass of the styrene-based block copolymer is 20 parts by mass or more and 100 parts by mass or less, the curing agent is a phenol-based curing agent, and the curing accelerator is 1-cyanoethyl-2. -A hot melt adhesive sheet that is ethyl-4-methylimidazole. The two members are interposed between the members to be bonded, and are used by adhering one side to the first member of the members and adhering the other side to the second member.
The surface of the two members to be adhered to the one-sided side and the other-sided side is formed of a resin composition, and the first resin composition and the first resin composition forming the surface of the first member. The hot melt adhesive sheet according to claim 3 , wherein the second resin composition forming the surface of the second member has a different polarity from the second resin composition.

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