JP3476248B2 - Hot melt type adhesive containing bubbles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-melt pressure-sensitive adhesive containing bubbles which is excellent in removability, low-temperature properties and adhesion to rough surfaces. 2. Description of the Related Art Most of hot-melt type pressure-sensitive adhesives conventionally used are polystyrene / polyisoprene-based block copolymers, polystyrene / polybutadiene-based block copolymers and hydrogenated products thereof as elastomers. And a blend of a tackifier resin, a softener, an antioxidant, and the like.
However, since this adhesive has an excessively strong adhesive force and does not have removability, when the adhesive tape using the adhesive is peeled off, there is a defect that the adherend is damaged or the tape is cut. In addition, since the cohesive force is too strong, there have been problems such as inferior low-temperature characteristics and poor adhesion to rough surfaces. On the other hand, there has been proposed a hot-melt type pressure-sensitive adhesive or adhesive which is improved in quality by foaming. For example, Japanese Patent Publication No. 50-1466
No. 8, JP-A-58-125776 aims to improve the adhesion to rough surfaces by including bubbles in the pressure-sensitive adhesive. However, with these methods,
There is a drawback that bubbles are crushed or disappear over time. In order to improve the stability of the bubbles in the pressure-sensitive adhesive, Japanese Patent Publication No. 64-6678 discloses that the bubbles in the pressure-sensitive adhesive are reduced by at least 5% from the volume at the time of the formation of the bubbles. However, it is difficult to set conditions to reduce 5% and poor reproducibility,
It is not practical because bubbles are crushed by the shear stress generated in the adhesive at the time of application of the adhesive, and the bubbles cannot be uniformly dispersed. Further, Japanese Patent Application Laid-Open No. 63-89582 proposes a method for improving the stability of a pressure-sensitive adhesive or bubbles in an adhesive by including hollow glass microspheres having a diameter of 200 μm or less. However, the glass microspheres proposed by the method generally have a non-uniform sphere diameter.
Therefore, for example, when the thickness of the adhesive is applied to 100 μm, using glass microspheres having an average particle diameter of 100 μm,
A sphere with a particle size larger than the average particle size will cause clogging in the coating head, and impede the coating properties of the adhesive,
Even when a streaky adhesive is not applied to the surface of the adhesive, that is, when a so-called dust streak is formed, or when the adhesive is applied together with the adhesive without causing clogging, a sphere having a particle size larger than the thickness of the adhesive is applied to the adhesive surface. And the smoothness of the surface of the pressure-sensitive adhesive is impaired, and the pressure-sensitive adhesive properties deteriorate. In this case, the problem can be solved by using glass microspheres having a small sphere having a maximum sphere diameter of less than 100 μm, but there is a disadvantage that the effect of improving the stability of bubbles is weakened. In any case, when air bubbles are contained in a pressure-sensitive adhesive or an adhesive, a method for achieving both the improvement of the characteristics of the pressure-sensitive adhesive or the adhesive and the improvement of the stability of the air bubbles over time with good reproducibility is as follows. There is no present. SUMMARY OF THE INVENTION An object of the present invention is to provide a hot-melt pressure-sensitive adhesive containing bubbles, which is excellent in removability, low-temperature properties and adhesion to rough surfaces. Here, the term "removability" means that there is no phenomenon that the adherend is damaged or the tape is cut when the adhesive tape is peeled off. The present invention relates to a hot-melt pressure-sensitive adhesive containing air bubbles, wherein a solid inorganic filler having an average particle diameter of not more than 200 μm is contained in the pressure-sensitive adhesive in an amount of 2 to 30% by weight. % Hot-melt pressure-sensitive adhesive. In the present invention, examples of non-hollow massive inorganic fillers used for the purpose of improving the stability of air bubbles include calcium carbonate, magnesium carbonate, titanium oxide, and talc, but calcium carbonate is preferred. . The average particle size is preferably 200 μm or less, as described later in the section of “Action”. The addition amount of the inorganic filler is preferably 2 to 30% by weight in the pressure-sensitive adhesive. If it is less than 2% by weight, the stability of the bubbles in the pressure-sensitive adhesive will be poor. Also, 30
If the amount is more than 10% by weight, the pressure-sensitive adhesive becomes hard, and the adhesion to a rough surface and the low-temperature characteristics are reduced. In the present invention, a foaming agent is used to contain air bubbles in the adhesive. Examples of the foaming agent include a chemical decomposition-type foaming agent that generally generates a decomposition gas such as nitrogen, carbon dioxide, and water vapor by heating. Specifically, “Uniform” of Otsuka Chemical Co., Ltd. and “Uniform” of Eiwa Chemical Co., Ltd. Vinyform "and the like. The bubbles formed by the foaming agent are preferably 5 to 40 vol% of the total volume of the pressure-sensitive adhesive. If it exceeds 40 vol%, the cohesive strength and adhesive strength of the pressure-sensitive adhesive are significantly reduced. If the content is 5 vol% or less, the effect of containing bubbles is poor, so that the adhesion to the rough surface and the low-temperature characteristics are deteriorated, and the removability is reduced. The composition of the hot melt pressure-sensitive adhesive used in the present invention is not particularly limited, but generally, a pressure-sensitive adhesive containing a thermoplastic block copolymer as a main elastomer is used. The block copolymer is generally represented by an AB type or an ABA type, wherein A is a polymer block of an aromatic vinyl monomer, and B is a polymer of a conjugated diene monomer. Indicates a block. Examples of such block copolymers include styrene-isoprene block copolymer, styrene-butadiene block copolymer, and AB-
A-type styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer and hydrogenated styrene-ethylene-propylene-styrene block copolymer, styrene-
Examples thereof include thermoplastic elastomers such as an ethylene-butylene-styrene block copolymer. These elastomers are blended with a tackifier resin, a softener, an antioxidant, and an ultraviolet absorber. Examples of the tackifying resin include known resins such as an aliphatic petroleum resin, an aromatic petroleum resin, a rosin resin, a terpene resin, and a cumarone / indene resin. Examples of the softener include naphthenic oils, aromatic oils, paraffinic oils, and the like. Antioxidants such as bisphenol-based and triazine-based antioxidants are exemplified. A polyethylene-based elastomer component;
Known polyolefin-based elastomers such as polypropylene-based and ethylene-vinyl acetate copolymers may be used within a range not exceeding 20% by weight of the total elastomer. When the solid bulk inorganic filler of the present invention is used, even if the inorganic filler has a non-uniform particle size and a lump having a particle size larger than the thickness of the pressure-sensitive adhesive is mixed, the pressure-sensitive adhesive is not affected. Due to the shearing force at the time of application of the adhesive, the filler agglomerate is broken within a range not exceeding the thickness of the applied adhesive, and does not protrude onto the surface of the adhesive. However, when the particle size of the inorganic filler is much larger than the thickness of the pressure-sensitive adhesive, the inorganic filler is hard to be completely destroyed even by the shearing force at the time of applying the pressure-sensitive adhesive, and as a result,
The filler particles protrude from the surface of the pressure-sensitive adhesive. In general, the thickness of the pressure-sensitive adhesive of the pressure-sensitive adhesive tape hardly exceeds 200 μm. Therefore, the average particle size of the inorganic filler used in the present invention is preferably 200 μm or less. The mechanism by which air bubbles disappear with the passage of time is based on the fact that the air bubbles move in the adhesive, become larger by coalescence, and scatter outside the adhesive, but contain a filler. This suppresses the movement of bubbles in the adhesive, and stabilizes the bubbles. Note that Japanese Patent Application Laid-Open
In the case of using hollow glass microspheres disclosed in Japanese Patent Application Laid-Open No. 3-89582, the microspheres are broken by a shearing force inside the pressure-sensitive adhesive at the time of application of the pressure-sensitive adhesive, and become thin scale-like. Is inferior to the filler of the present invention. The present invention will be described in detail with reference to examples, but the present invention is not limited to the examples. Example 1 A base adhesive having the following composition was prepared by melting and stirring at 195 ° C. Base adhesive composition (A) Styrene-isoprene block copolymer ^{* 1)} 100 parts by weight (B) Aliphatic petroleum resin ^{* 2)} 70 parts by weight (C) Coumarone / indene resin ^{* 3)} 35 parts by weight (D ) Naphthenic oil ^{* 4)} 50 parts by weight (E) 1 part by weight of bisphenol-based antioxidant * 1): Kariflex TR1107 (manufactured by Shell Chemical Co., Ltd.) * 2): Quinton D100 (manufactured by Zeon Corporation) * 3): Escron G90 [manufactured by Nippon Steel Chemical Co., Ltd.] * 4): Shellflex 371N [manufactured by Shell Chemical Co., Ltd.] 50 parts by weight of calcium carbonate (trade name; cold water # 100, Nitto Powder Chemical Co., Ltd.) in 15 parts by weight (13.0% by weight) with respect to 100 parts by weight of the adhesive, and a uniform as a pyrolytic foaming agent AZ-L
[Otsuka Chemical Co., Ltd.]] was added in an amount of 0.5 part by weight based on 100 parts by weight of the adhesive, and the mixture was stirred and melted to prepare a hot-melt adhesive composition containing bubbles. The bubble-containing hot melt type pressure-sensitive adhesive obtained according to the above, on a hot plate,
The polyester was melt-coated on a 38 μm thick polyester film so that the thickness of the pressure-sensitive adhesive was 55 μm. Example 2 Calcium carbonate having an average particle size of 65 μm (trade name; cold water # 70, Nitto Powder Chemical Industry Co., Ltd.) was added to the base pressure-sensitive adhesive melt used in Example 1 as a solid inorganic filler. Adhesive 1
15 parts by weight (13.0% by weight) to 00 parts by weight and 0.5 parts by weight of the decomposable foaming agent used in Example 1 to 100 parts by weight of the adhesive were added, and the mixture was melt-stirred at 195 ° C. Thus, a hot-melt pressure-sensitive adhesive composition containing bubbles was prepared. The bubble-containing hot melt type pressure-sensitive adhesive obtained as described above was melt-coated on a 38 μm-thick polyester film on a hot plate so that the pressure-sensitive adhesive thickness was 70 μm. Comparative Example 1 In place of the inorganic filler used in Example 1, inorganic hollow particles having an average particle diameter of 49 μm [trade name: Microcells S
L-75, manufactured by Onoda Cement Co., Ltd.]. Comparative Example 2 In place of the inorganic filler used in Example 2, inorganic hollow particles having an average particle diameter of 65 μm [trade name;
/ 7, manufactured by Nippon Philite Co., Ltd.]. Comparative Example 3 The same operation as in Example 1 was performed, except that the inorganic filler and the foaming agent were not used. The pressure-sensitive adhesive thicknesses of the pressure-sensitive adhesive tapes obtained in Examples 1 and 2 and Comparative Examples 1 to 3 were examined before normal aging and after aging for one month at 40 ° C. Further, the adhesive strength, removability, low-temperature properties, and adhesion to rough surfaces were tested by the following test methods. According to JIS Z0237, an adhesive tape having a width of 25 mm is adhered to a stainless steel panel in an atmosphere of 23 ° C., and is reciprocated by a 2-kg rubber roll at a speed of 300 mm / min. A peeling force of 300 mm / min was measured. Adhesive tape was applied to decorative plywood in an atmosphere of 23 ° C.
Two reciprocal presses at a speed of 300 mm / min.
It peeled rapidly at a peeling angle of 80 degrees, and the peeling state of the painted surface of the decorative plywood was observed. Those with no paint peeling have re-peelability. Low Temperature Characteristics (Ball Tack Value, Adhesion to Cardboard) As an index of low temperature characteristics, the ball tack value at 5 ° C. and the adhesion to cardboard were tested by the following test methods. Ball tack value According to the DOW method, a tilt angle of 3 in a 5 ° C atmosphere
On a 0 ° stainless steel plate, attach a 10 cm long adhesive tape with the adhesive side up and 10 cm from the top of the adhesive tape.
From the position, 30 types of steel balls having a diameter of 3/32 to 1 inch were rolled at an initial speed of 0, and the number of the largest steel ball stopped on the adhesive tape was taken as the ball tack value. The larger the ball tack value, the higher the initial adhesiveness. Adhesion to cardboard K liner After leaving the cardboard and the adhesive tape in an atmosphere of 5 ° C. for 1 hour or more, the adhesive tape is attached to the cardboard,
One pressure reciprocation was performed under a load of 850 g, and the film was rapidly peeled immediately at a peeling angle of 180 °. The degree of peeling of the cardboard paper surface was expressed as a percentage (%) with respect to the adhesive tape application area.
In addition, the characteristic is so good that the corrugated paper stripping rate is large. Adhesive tape with a rough surface Affixing a 25 mm wide adhesive tape to a concrete block in an atmosphere of 23 ° C., and pressing it back and forth once at a speed of 300 mm / min with a 2 kg rubber roll, leaving it for 20 minutes, and then leaving it at a peel angle of 180 °
The peel force was measured at a peel rate of 300 mm / min. Test Results The results obtained by the above tests are shown in Table 1. [Table 1] As is clear from Table 1, Examples 1 and 2 are excellent in removability, low-temperature properties, and adhesion to rough surfaces, have little change in the thickness of the pressure-sensitive adhesive, and have good bubble stability. It is. On the other hand, in Comparative Examples 1 and 2, although the change in thickness is relatively small and the stability of air bubbles is good, hollow particles protrude from the surface of the pressure-sensitive adhesive or hollow particles having a particle diameter larger than the average particle diameter. In addition, clogging occurs at the tip of the coating device, and streak-like dust lines to which the pressure-sensitive adhesive is not applied occur, resulting in poor adhesion characteristics. In Comparative Example 3, which consists only of the base adhesive containing no filler and no air bubbles, there is no removability, and the low-temperature properties and the adhesion to rough surfaces are poor. According to the present invention, the inorganic filler has a non-uniform particle size, and even if a filler having a particle size larger than the thickness of the adhesive is mixed, the surface of the adhesive is smooth. , And the collapse and disappearance of bubbles in the adhesive can be prevented. The maintenance of the smoothness and the prevention of the disappearance of the bubbles bring about excellent effects in the low-temperature characteristics, the adhesion to the rough surface and the removability of the bubble-containing hot-melt adhesive. By applying the bubble-containing hot-melt type pressure-sensitive adhesive according to the present invention to a film, kraft paper, cloth base material, or the like, a pressure-sensitive adhesive tape having excellent properties in packing use, temporary fixing of building materials, and the like can be obtained.

Continuation of front page (72) Inventor Tsunetaka Sakurai 2-4-2 Kudanminami, Chiyoda-ku, Tokyo Nichiban Co., Ltd. (72) Inventor Kinnosuke Hino 2-4-2 Kudanminami, Chiyoda-ku, Tokyo Nichiban Inside (72) Inventor Kensei Takahashi 2-4-2 Kudanminami, Chiyoda-ku, Tokyo Nichiban Co., Ltd. (72) Inventor Hideyuki Nakajima 2-4-2 Kudanminami, Chiyoda-ku, Tokyo Nichiban Co., Ltd. (56) References JP-A-63-89582 (JP, A) JP-A-52-66545 (JP, A) JP-A-60-76583 (JP, A) JP-A-58-125776 (JP, A) 58-83074 (JP, A) JP 50-14668 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09J 1/00-201/10

Claims (1)

(57) [Claim 1] A hot-melt pressure-sensitive adhesive containing air bubbles, wherein the pressure-sensitive adhesive contains 2-30% by weight of a solid inorganic filler having an average particle size of 200 μm or less. Hot melt type adhesive containing bubbles.