JPH0765022B2 - Adhesive composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition having excellent low-temperature adhesiveness and high adhesiveness.

(Prior art) Recently, the problem of environmental pollution caused by solvent-based adhesives and adhesives has been taken up severely, and hot-melt type adhesive / adhesive has been widely used from the viewpoint of energy saving and resource saving. Is becoming. A block copolymer composed of styrene-conjugated diene-styrene is generally used as a base polymer of the hot-melt type adhesive / adhesive. However, the pressure-sensitive adhesive obtained using this block copolymer, since the block copolymer contains polystyrene, the adhesive performance at low temperature,
In particular, the adhesive strength is insufficient, and there is a problem with the adhesive strength when used in winter and cold regions, or when used for refrigerated or frozen products. Further, since this styrene-conjugated diene-styrene block copolymer has a high viscosity when melted due to aggregation of styrene moieties, a considerably high temperature is required for mixing and coating during hot melt. as a result,
This causes heat deterioration of the polymer, and the performance of the obtained pressure-sensitive adhesive becomes extremely low. In order to avoid heat deterioration due to high temperature, improve workability during hot melt, and further improve adhesive strength at low temperature, a method of adding a plasticizer such as process oil or a softening agent to the adhesive is usually used. It is adopted, and it is possible to reduce the melt viscosity and improve the adhesive strength at low temperature to some extent. However, adhesives containing process oil have poor cohesive strength at relatively high temperatures, oil bleeds from the adhesive and contaminates the base material or adherend of the adhesive, and changes in adhesive performance over time. There are problems such as being large. In addition, styrene-
The pressure-sensitive adhesive using a conjugated diene-styrene block copolymer does not always have sufficient adhesive force, particularly adhesive force to polyolefins, and its utilization range is limited at present.

(Problems to be Solved by the Invention) The object of the present invention is, therefore, at low temperature without impairing the excellent performance originally possessed by the hot-melt pressure-sensitive adhesive using the styrene-conjugated diene-styrene block copolymer. It is intended to provide a pressure-sensitive adhesive composition having improved adhesive properties and excellent adhesive strength.

(Means for Solving Problems) According to the present invention, the above object is a composition for pressure-sensitive adhesives containing a styrene-conjugated diene-styrene block copolymer and a conjugated diene-styrene-conjugated diene block copolymer. Is achieved by providing.

The styrene-conjugated diene-styrene block copolymer used in the present invention is styrene-isoprene-
In addition to the styrene copolymer styrene-butadiene styrene copolymer and the like, those obtained by partially or completely hydrogenating the diene portion of these copolymers and the like can be mentioned. Of these, a styrene-isoprene-styrene block copolymer is preferably used. The conjugated diene-styrene-conjugated diene block copolymer is isoprene, butadiene,
A block-shaped polymer composed of a polymer portion composed of one or more kinds of conjugated diene-based monomers such as piperylene and a polymer portion of styrene, having a molecular weight of 10,0.
The weight ratio of 00 to 70,000 styrene and conjugated diene
Generally, 5/95 to 50/50 and a conjugated diene moiety having a 1,4 bond content of 70% or more are used. If the molecular weight of the diblock copolymer is less than 10,000, the performance of the obtained pressure-sensitive adhesive will be low and bleeding will be easy, while if it exceeds 70,000, the plasticizing effect will be poor and workability will not be improved. Moreover, the effect of improving the low temperature characteristics is not observed. When the weight ratio of styrene / conjugated diene is less than 5/95, bleeding tends to occur, and when it exceeds 50/50, the low temperature characteristics are rather deteriorated, which is not preferable. When the 1,4 bond content of the conjugated diene portion of the conjugated diene-styrene-conjugated diene block copolymer is less than 70%, the polymer becomes a hard polymer and there is no effect of improving the low temperature properties, and the adhesive properties are impaired. It is not desirable.

Such a conjugated diene-styrene-conjugated diene block copolymer can be easily obtained by an anionic polymerization method. As an example, using alkyl lithium as a catalyst,
It can be obtained by sequentially polymerizing a conjugated diene, styrene and a conjugated diene in this order, or a polymer obtained by polymerizing a conjugated diene and styrene in this order is combined by a suitable method to form a conjugated diene-styrene-conjugate. It can also be a diene type. It is also possible to obtain a conjugated diene-styrene-conjugated diene type block copolymer by polymerizing styrene and a conjugated diene in this order using a bifunctional alkyllithium catalyst. As the diene component of this block copolymer, isoprene is most suitable from the viewpoint of adhesive properties.

The styrene-conjugated diene-styrene block copolymer and the conjugated diene-styrene-conjugated diene block copolymer are usually used in a weight ratio of 97/3 to 60/40. If the use ratio of the conjugated diene-styrene-conjugated diene block copolymer to the styrene-conjugated diene-styrene block copolymer is smaller than the above range, the effect of improving the adhesive property cannot be obtained, and the same use ratio is within the above range. If it exceeds, it is difficult to obtain a pressure-sensitive adhesive composition having sufficient adhesive performance.

If necessary, a tackifying resin or other compounding agent may be added to the composition for pressure-sensitive adhesives of the present invention. There is no particular limitation on the amount and type of tackifying resin in this case,
One type or two or more types are added in an appropriate amount depending on the required performance of the pressure-sensitive adhesive. As the compounding agent, an antioxidant, an ultraviolet absorber, and a filler such as calcium carbonate or titanium oxide are used. It is also possible to add a process oil and a low molecular weight polymer of a conjugated diene together as a plasticizer as long as the amounts do not impair the gist of the present invention. In this case, the amount of these plasticizers used is preferably half or less of the weight of the conjugated diene-styrene-conjugated diene block copolymer.

The composition for pressure-sensitive adhesive of the present invention is melted and then applied to a substrate such as paper, cellophane, polypropylene and polyester, or dissolved in a solvent such as toluene and applied to an adherend in a solution state. Can be used.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Examples 1 to 7 and Comparative Example 1 Using n-butyllithium as a catalyst, isoprene, styrene and isoprene were sequentially added and polymerized to give a molecular weight, a styrene / isoprene ratio and a ratio shown in Table 1.
An isoprene-styrene-isoprene block copolymer having a 1,4 bond content was obtained. For comparison, an isoprene homopolymer having a molecular weight and a 1.4-bonding amount shown in Table 1 was obtained. These polymers and styrene-isoprene-styrene block copolymer (cariflex TR-1 manufactured by Shell Chemical Co., Ltd.)
107) was melt mixed at 180 ° C. according to the formulation shown in Table 2 to prepare an adhesive composition. An adhesive tape was prepared by applying this composition to a polyester film, and the adhesive properties were evaluated. Evaluation of adhesive performance is JIS-Z-023
7. The low temperature characteristics were evaluated by measuring the ball tack at 10 ° C. The bleed condition is 70 ° C when the adhesive tape and high quality paper are pasted together.
After heating for 2 weeks, the evaluation was made based on the presence or absence of bleeding on the high-quality paper.

(Effect of the invention) According to the present invention, the adhesive performance at low temperature and the adhesive strength to polyolefins are excellent, and there is no fear of bleeding,
Furthermore, a pressure-sensitive adhesive composition effective for improving workability during mixing and coating is provided.

Claims (4)

[Claims] 1. A pressure-sensitive adhesive composition containing a styrene-conjugated diene-styrene block copolymer and a conjugated diene-styrene conjugated diene block copolymer. 2. A conjugated diene-styrene-conjugated diene block copolymer having a molecular weight of 10,000 to 70,000 and a ratio of styrene to a conjugated diene in a weight ratio of 5/95 to 50/50. The composition for pressure-sensitive adhesives according to the item. 3. The pressure-sensitive adhesive composition according to claim 1, wherein the conjugated diene portion of the conjugated diene-styrene-conjugated diene block copolymer has a 1,4 bond content of 70% or more. 4. The pressure-sensitive adhesive according to claim 1, wherein the weight ratio of the styrene-conjugated diene-styrene block copolymer to the conjugated diene-styrene-conjugated diene is 97/3 to 60/40. Composition.