JPH05345885A - Tacky agent and adhesive composition - Google Patents

Abstract

PURPOSE:To obtain a tacky agent and adhesive composition having excellent thermal stability. CONSTITUTION:A thermoplastic elastomer which comprises at least two polymer blocks consisting essentially of a vinyl aromatic compound and at least one polymer block of a mixed system of butadiene and isoprene, having 10-90wt.% isoprene content and has 5-50wt.% content of blocks consisting essentially of the vinyl aromatic compound is used as an essential component for a tacky agent and adhesive composition.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a viscous / adhesive composition having excellent heat stability.

[0002]

2. Description of the Related Art In recent years, the problem of viscous adhesives using solvents and environmental pollution of solvents has been taken up severely, and hot-melt type adhesives have been widely used from the viewpoint of energy saving and resource saving. ing. Conventionally, a styrene-isoprene-styrene block copolymer and a styrene-butadiene-styrene block copolymer have been generally used as a base polymer of this hot melt type adhesive / adhesive. However, these unhydrogenated styrenic block copolymers have a conjugated diene and thus have a markedly poor heat deterioration resistance. As a result, when a viscous / adhesive mixture using an unhydrogenated styrenic block copolymer as a base polymer is prepared by the melt kneading method, it is kneaded in an atmosphere of an inert gas such as nitrogen in order to suppress thermal deterioration. However, if kneading is performed for a long time, thermal deterioration cannot be completely prevented, and viscous / adhesive performance including melt viscosity of the obtained composition becomes unstable. Further, when kneading is performed under a nitrogen stream, a low molecular weight compound such as a plasticizer is volatilized, a composition having an accurate composition cannot be obtained, and the viscous / adhesive performance including the melt viscosity of the composition becomes unstable. ..

Therefore, when a viscous / adhesive mixture is prepared by a melt-kneading method using an unhydrogenated styrene block copolymer as a base polymer, a large amount of tackifying resin, plasticizer, etc. are used in order to shorten the kneading time. Alternatively, a polymer having a low melt viscosity must be used as the base polymer, which greatly restricts the formulation. Furthermore, since the viscous / adhesive composition itself using an unhydrogenated styrene block copolymer as a base polymer is inferior in heat aging resistance, its change over time is large and its use is limited. Therefore, in order to satisfy the thermal stability during kneading and the thermal stability of the composition, a hydrogenated styrene block copolymer may be used as the base polymer. However, since the melt viscosity of the hydrogenated product is generally higher than the melt viscosity of the unhydrogenated styrene block copolymer, a viscous / adhesive composition using the hydrogenated styrene block copolymer as a base polymer. Has the disadvantage of poor workability. In addition, hydrogenated styrenic block copolymers have less compatibility with various tackifying resins and plasticizers than those of unhydrogenated styrenic block copolymers, and their formulation is very limited. Has been done. As a result, at present, a viscous / adhesive composition using an unhydrogenated styrene block copolymer having excellent heat aging resistance is desired.

[0004]

An object of the present invention is to obtain a viscous / adhesive composition using an unhydrogenated styrene block copolymer having improved heat aging resistance.

[0005]

According to the present invention, the above-mentioned object is to provide a mixed system of at least two polymer blocks mainly containing a vinyl aromatic compound and butadiene and isoprene and having an isoprene content of 10 to 90 wt. % Of at least one polymer block, which is achieved by a viscous / adhesive composition containing a thermoplastic elastomer containing 5 to 50 wt% of the vinyl aromatic compound-based block. ..

The vinyl aromatic compound used in the present invention is styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene,
There are vinyl anthracene and the like, but styrene is particularly common. These may be used alone or in combination of two or more. The molecular weight of the polymer block mainly composed of vinyl aromatic compound is 4,000 to 5
It is 50,000, preferably 5,000 to 30,000.

The polymer block composed of a mixed system of butadiene and isoprene has an isoprene content of 10 to 90 w.
It needs to be t%. Isoprene content is 1
If it is less than 0% by weight, the viscosity of the composition decreases during melt kneading,
When the isoprene content exceeds 90 wt%, the viscosity of the composition increases during melt kneading, and a stable composition cannot be obtained in terms of viscosity and physical properties. The molecular weight of the block composed of a mixed system of butadiene and isoprene is 10,000 to 500,0.
00, preferably 50,000 to 200,000.

It is necessary that the content of the block mainly composed of the vinyl aromatic compound is 5 to 50 wt%. If this ratio is less than 5 wt%, the cohesive force of the resulting composition is low, and as a result, the desired creep resistance cannot be obtained. If it exceeds 50 wt%, the adhesiveness is poor.

The block copolymer used in the present invention can be easily obtained by an anionic polymerization method. As an example, using alkyl lithium as a catalyst, a method of sequentially polymerizing a vinyl aromatic compound block and a block of a mixed system of butadiene and isoprene, or a block of a mixed system of a vinyl aromatic compound block and butadiene, isoprene, respectively. After the polymerization, a method of connecting these polymer blocks by a suitable method can be mentioned. Regarding the bonding mode of the polymer block composed of butadiene and isoprene, any mode such as one in which isoprene and butadiene are bonded in a block shape, one in which they are randomly bonded, or one in which they are taper-shaped may be used. ..

If desired, a tackifying resin, a plasticizer or other compound may be added to the viscous / adhesive composition of the present invention. In this case, the tackifying resin and the plasticizer are not particularly limited and may be blended depending on the required viscosity / adhesive performance. As the compounding agent, an antioxidant, an ultraviolet absorber, and a filler such as calcium carbonate or titanium oxide are used. Moreover, you may mix | blend other unhydrogenated styrene block copolymers and hydrogenated styrene block copolymers in the range which does not impair the meaning of this invention.

The adhesive / adhesive composition of the present invention is melted and then applied to a base such as paper, cellophane, polypropylene or polyester, or dissolved in a solvent such as toluene to be adhered to an adherend in a solution state. It is used as a coating.

[0012]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto as long as the gist of the present invention is not exceeded. (Examples 1 to 4) Styrene-isoprene / butadiene-styrene block copolymers shown in Table 1 were prepared by polymerizing styrene using n-butyllithium as a catalyst, polymerizing a mixed monomer of isoprene and butadiene, and then adding and polymerizing styrene. A polymer was obtained. An adhesive composition was obtained by melt-mixing these block copolymers with a kneader sufficiently substituted with nitrogen according to the formulation shown in Table 2 at 170 ° C. The thermal stability of the composition was evaluated by the change in melt viscosity before and after the composition was left standing in a gear oven at 150 ° C. for 12 hours. The results are shown in Table 2. Melt viscosity is 130
Shear rate 6.1 x 10 ² with ℃ capillary rheometer
The case of (1 / sec) was defined as the melt viscosity. A pressure-sensitive adhesive tape was produced by applying this pressure-sensitive adhesive composition to a polyester film, and the adhesive strength and holding power were evaluated. The results are shown in Table 2. Adhesive strength: Adhesive tape is adhered to SUS304 plate, 180 ° angle at ambient temperature 25 ° C, and pulling speed 300 mm
It was peeled off at a rate of / minute. Holding power is 25mm on SUS304 plate
Adhesion was performed at × 25 mm, a load of 1 kg was suspended at an environmental temperature of 40 ° C., and the drop time was determined. (Comparative Examples 1 and 2) Two kinds of styrene-isoprene / butadiene-styrene block copolymers having 5% by weight and 95% by weight of isoprene in the block composed of the mixed system of isoprene and butadiene were prepared in the same manner as in Examples 1 to 4. Then, a composition was prepared in the same manner as in Examples 1 to 4 except that these block copolymers were used to prepare an adhesive tape. When the physical properties were measured, they were poor in thermal stability. (Comparative Examples 3 to 4) Two types of styrene-isoprene / butadiene-containing isoprene / butadiene-containing blocks having an isoprene content of 45 wt% and a styrene content of 2 wt% and 65 wt% as in Examples 1 to 4. Styrene block copolymers were prepared, compositions were prepared in the same manner as in Examples 1 to 4 except that these block copolymers were used, adhesive tapes were prepared, and physical properties were measured. These had poor holding power and adhesive strength. (Comparative Example 5) A styrene-isoprene-styrene block copolymer and a styrene-butadiene-styrene block copolymer shown in Table 1 were prepared, and those blended at a ratio of 1/1 were used as a base polymer. 1 to
A composition was prepared in the same manner as in 4 to prepare an adhesive tape,
The physical properties were measured. This composition caused phase separation after the heat deterioration test and lacked heat stability.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

The present invention provides a viscous / adhesive composition having excellent thermal stability.

Claims (1)

[Claims] 1. At least two polymer blocks mainly containing a vinyl aromatic compound, and at least one polymer block having a isoprene content of 10 to 90 wt% in a mixed system of butadiene and isoprene. , The content ratio of the block mainly composed of the vinyl aromatic compound is 5 to 5
A viscous / adhesive composition comprising 0 wt% of a thermoplastic elastomer.