JP2002121524A - Hot-melt adhesive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hot-melt adhesive which has high creep resistance and can adhere to a plurality of materials and can cope with a plurality of coating methods. SOLUTION: A hot-melt adhesive composition comprises a thermoplastic block copolymer having structures of (a) (A1-B1)n1M (n1 is a natural number of >=2; and M is a residue or residual group of a polyfunctional compound to which n1 polymer chains have been bonded) (a coupling agent), (b) A2-(B2-A3)n2 (wherein n2 is a natural number), (c) (B3-A4)n3 (wherein n3 is a natural number of >=2), (d) B4-(A5-B5)n4 (wherein n4 is a natural number), and (e) A6-B6 [provided that A1, A2, A3, A4, A5, and A6 are each a vinyl aromatic hydrocarbon polymer block having a glass transition point (Tg) of >=room temperature; and B1, B2, B3, B4, B5, and B6 are each a butadiene polymer block], a hydrogenated terpene resin which is solid at room temperature, a 5C based hydrogenated resin which is liquid at room temperature, and a plastifying oil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-melt adhesive, and more particularly to a hot-melt adhesive suitable for bonding not only olefin sheets but also pulp, pulp fiber compacts, cellulose products such as paper products, or disposable diapers and sanitary products. An adhesive composition which is used for disposable articles such as napkins, paper packaging, and the like.

[0002]

2. Description of the Related Art Conventionally, rubber-based hot melt adhesives containing a thermoplastic block polymer as a main component (JP-A-4-351689) and synthetic olefins (for example, ethylene-propylene-butene copolymer, ethylene- Olefin-based hot melt adhesives whose main component is vinyl acetate copolymer) have been widely used. Above all, rubber-based hot melt adhesives have excellent adhesiveness to polyolefin-based materials, and have high adhesion, cohesion, and creep resistance. Used as an adhesive for nonwoven fabrics. In particular, in the diaper or sanitary napkin, at the leak-prevention site called gather, an elastic body with elasticity is used as the material, and since high creep resistance is required for adhesion at this site, A rubber-based hot melt adhesive is often used for bonding.

However, in recent years, the application method of hot melt adhesives has been diversified, and various application methods such as spiral spray, curtain spray, slit coating, and control seam spray have been adopted for the gathers described above. In addition, different materials such as polyurethane elastic yarn and natural rubber are also used for the elastic material, and it is necessary to design different hot melt adhesives depending on the elastic material used and the coating method. is there. Recently, as described above, adhesives designed according to the type of elastic material and coating method are often used, so there are many types of hot melt adhesives to be used, and it is necessary to increase the number of melting tanks accordingly There is a problem that inventory management becomes complicated. Further, various materials have been tried for disposable diapers and sanitary napkins, and methods for applying a hot-melt adhesive have also been improved.
However, as the material and the coating method are changed, the hot-melt adhesive that has been used before can often not be used, and there is a problem that the adhesive must be newly selected in practice.

Accordingly, a single type of hot melt adhesive is used to form a plurality of materials for such gathers, in particular, elastic materials of different materials such as polyurethane elastic yarn and natural rubber, spiral spray, curtain spray, slit coating, control seam. There is a strong demand for hot melt adhesives that can support different coating methods such as spraying.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a hot-melt adhesive which can bond a plurality of materials and can cope with a plurality of coating methods. Another object of the present invention is to provide a hot melt adhesive composition having high creep resistance.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, it has been found that an adhesive composition having the following constitution is effective. Thermoplastic block copolymer of the specific structure shown below, at room temperature solid hydrogenated terpene resin, liquid at room temperature C ₅ based hydrogenated resin, a hot melt adhesive composition comprising a plasticizing oil.

The above-mentioned thermoplastic block copolymer is a thermoplastic block copolymer comprising one or more selected from the following formulas a) to e). a) (A1-B1) _n1 M (n1 is a natural number of 2 or more, M is n
B) A2- (B2-A3) _n2 (n2 is a natural number) c) (B3-A4) _n3 (n3 D) B4- (A5-B5) _n4 (n4 is a natural number) e) A6-B6 (however, A1, A2, A3, A4, A5, and A6 are glass transition points (Tg) above room temperature) B1, B2, B3, B4, B5, B
6 is a butadiene polymer block, A1 to A6, B
1 to B6 may have the same molecular weight or different molecular weights. )

The content of the vinyl aromatic hydrocarbon in the thermoplastic block copolymer is preferably from 15 to 45% by weight. If the content of the vinyl aromatic hydrocarbon is less than 15%, the cohesive strength is too low, and the creep resistance is reduced. If the content exceeds 45% by weight, the initial tackiness is insufficient.

The above-mentioned vinyl aromatic hydrocarbon monomers include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene and the like. And styrene is particularly common. These may be used alone or in combination of two or more.

The hydrogenated terpene resin which is solid at room temperature is:
Chemical formula _{(C 5 H 8) n (} n is a natural number) obtained by homo- or copolymer terpenes represented by those obtained by copolymerizing with these terpenes and aromatic monomers, or those obtained by hydrogenating any foregoing It is. The softening temperature of the hydrogenated terpene resin that is solid at room temperature is preferably from 85 to 125 ° C, more preferably from 90 to 120 ° C. Softening temperature 90
If the temperature is lower than 120 ° C., the cohesive force of the adhesive tends to decrease, and
This is because if it exceeds 300 g, the adhesive tends to become hard and brittle.

The room temperature liquid C ₅ hydrogenated resin is a room temperature liquid resin obtained by polymerizing and hydrogenating a C ₅ fraction obtained by decomposing naphtha, and having a number average molecular weight. Is preferably 100 to 500. When the number average molecular weight is less than 100, the tack at room temperature becomes too large, and when it exceeds 500, the wettability to the adherend decreases.

The plasticizing oil is a paraffinic oil,
Naphthene-based and aroma-based are listed, and one or more of these may be used in combination. However, they are used in the present invention in consideration of cohesion, heat stability, odor and the like. More preferably, the plasticizing oil has an aroma component of 5% by weight or less and a naphthene component of 30% by weight or more. When the aroma content exceeds 5% by weight, the adhesive strength is reduced due to the odor and the remarkable decrease in cohesive strength. When the naphthene component is less than 30% by weight, the compatibility with the thermoplastic block copolymer is remarkably reduced, and problems such as bleed out become remarkable. Further, those containing a paraffin component as a component other than the naphthene component and the aroma component are preferable.

The mixing ratio of each component constituting the hot melt adhesive composition is 50 to 400 parts by weight of a hydrogenated terpene resin which is solid at room temperature and 100 parts by weight of a thermoplastic block copolymer. C ₅ based hydrogenated liquid resin 10
To 200 parts by weight, and 10 to 200 parts by weight of a plasticizing oil. More preferably, hydrogenated terpene resin 70 which is solid at room temperature
350 parts by weight, C ₅ based hydrogenated resin liquid at room temperature 20 to 1
80 parts by weight and 20 to 180 parts by weight of plasticizing oil.
If the amount of the hydrogenated terpene resin is less than the above,
If the hardness of the adhesive itself is insufficient or too high, the adhesive composition becomes brittle, which is not preferable. In the case of a hot-melt adhesive used for this type of application, an appropriate range of melt viscosity, hardness, cohesive strength, and the like are important, but sufficient properties can be obtained within the above ranges. C at room temperature
_{When the} amount of the pentahydrogenated resin is less than the above, the adhesive strength at room temperature is insufficient. If the amount of the plasticizing oil is less than the above-mentioned amount, the melt viscosity of the adhesive composition becomes too high, so that precise coating cannot be performed. Is more likely not to be available. Conversely, a large amount is not preferable because the cohesive force of the hot melt adhesive is significantly reduced.

Further, the hot melt adhesive composition includes
As appropriate, various heat stabilizers such as phenol-based, phosphorus-based, and sulfur-based, an antioxidant, and an ultraviolet absorber may be added.

As a method for producing the composition of the present invention, the above-mentioned components may be simply stirred and mixed in a container while heating, or may be a roll, a Banbury mixer, a kneader, or an extruder usually used for mixing a resin composition. A machine can also be used.

[0016]

(Adhesive strength)

(Sample preparation) A coating temperature of 140 ° C and a coating amount of 0.05 were applied to a polyethylene film mainly used for disposable diapers.
A sample was prepared by applying a bead at g / m and bonding the nonwoven fabric. (Evaluation) After the bonded test piece was left in an atmosphere of 20 ° C. for 24 hours, the test piece was taken out, the adherend was peeled off by hand, and the adhesion was evaluated according to the following criteria. ○: Material fracture △: Partial material fracture ×: Interfacial peeling or cohesive failure of adhesive

[Elastic Body Holding Force I] (Preparation of Sample) An adhesive is applied to a polyethylene film mainly used for a disposable diaper under the following conditions, and a natural rubber thread is stretched twice and adhered. Were adhered to obtain a sample. 1) Spiral spray (manufactured by Nordson) Coating temperature: 140 ° C., coating amount 15 g / m ² , spiral diameter: 20 mm 2) Curtain spray (manufactured by Sun Tool Co.) Application temperature: 140 ° C., coating amount: 7 g / m ² 3) Slit coating (manufactured by Suntool Co., Ltd.) Coating temperature: 140 ° C., coating amount: 0.05 g / m 4) Control seam spray (manufactured by Nordson) Coating temperature: 140 ° C., coating amount: 0.05 g / m m

(Evaluation) After the coating was left for one day, the coated sample was fixed at both ends in an atmosphere of 20 ° C. in a taut state, and oily oil was applied to a place where the length of the natural rubber became 20 cm. A mark was made with a pen, the natural rubber was cut at the mark, and the contracted length of the natural rubber after standing for 1 hour was measured. The retention was calculated from the following formula based on the measured value, and determined based on the following evaluation criteria. …: Retention rate: 70% to 100% △: Retention rate: 50% to 70% ×: Retention rate: 0% to 50%

[Elastic Body Holding Force II] The elastic body holding force I was the same as the elastic body holding force I except that the natural rubber thread having the elastic body holding force I was changed to polyurethane thread rubber. The results are shown in Table 1.

[0020]

[Table 1]

[0021]

The hot-melt adhesive composition of the present invention comprises:
Since it contains a thermoplastic block copolymer having the above specific structure, a hydrogenated terpene resin which is solid at room temperature, a C5-based hydrogenated resin which is liquid at room temperature, and a plasticizing oil, materials such as polyurethane elastic yarn and natural rubber It shows good adhesion to hands with different elastic materials, and can be applied by different coating methods such as spiral spray, curtain spray, slit coating, and control seam spray, and has high creep resistance.

Claims (1)

[Claims] 1. A method selected from the following formulas (a) to (e):
Species or two or more thermoplastic block copolymer, at room temperature solid hydrogenated terpene resin, room temperature C ₅ based hydrogenated liquid resin,
A hot melt adhesive composition comprising a plasticizing oil. a) (A1-B1) n1M (n1 is a natural number of 2 or more, M is
b) A2- (B2-A3) n2 (n2 is a natural number) c) (B3-A4) n3 (n3 is a natural number of 2 or more) d) B4- (A5-B5) n4 (n4 is a natural number) e) A6-B6 (where A1, A2, A3, A4, A5, and A6 are vinyl aromatic carbons having a glass transition point (Tg) of room temperature or higher. Hydrogen polymer block, B1, B2, B3, B4, B5, B
6 is a butadiene polymer block. )