JPH083523A - Bubble-containing hot melt adhesive - Google Patents

Abstract

PURPOSE:To provide a hot-melt tacky adhesive containing a specific amount of a granular inorganic filter free from hollow part and having specific particle diameter in a tacky adhesive agent, having excellent low-temperature characteristics, adhesion to rough surface and releasability and suitable for packaging use and temporary fixing of an architectural material, etc. CONSTITUTION:This bubble-containing hot-melt tacky adhesive contains (A) 2-30wt.% of a granular inorganic filler free from hollow part and having an average particle diameter of <=200mum (e.g. calcium carbonate, magnesium carbonate, titanium oxide or talc) in (B) a hot-melt tacky adhesive containing a styrene-isoprene block copolymer, a styrene-isoprene-styrene block copolymer, etc., as a main elastomer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bubble-containing hot-melt type pressure-sensitive adhesive having excellent removability, low temperature characteristics and adhesion to rough surfaces.

[0002]

2. Description of the Related Art Most of the hot-melt type pressure-sensitive adhesives that have been conventionally used are elastomers such as polystyrene / polyisoprene block copolymers, polystyrene / polybutadiene block copolymers, and block copolymers of these hydrogenated compounds. It is a blend of a polymer, a tackifying resin, a softening agent, an antiaging agent and the like.
However, since this adhesive has too strong an adhesive force and has no removability, it has a drawback that the adherend is damaged or the tape is cut when the adhesive tape using the adhesive is peeled off. Further, since the cohesive force is too strong, there are problems such as poor low temperature properties and poor adhesion to rough surfaces.

On the other hand, it has been proposed to improve the quality of hot-melt pressure-sensitive adhesives or adhesives by foaming them. For example, Japanese Patent Publication No. 50-1466
In Japanese Patent Laid-Open No. 8 and Japanese Patent Laid-Open No. 58-125776, it is aimed to improve the adhesiveness to rough surfaces by including bubbles in the pressure-sensitive adhesive. However, with these methods,
There is a drawback that air bubbles collapse or disappear over time.

Further, in order to improve the stability of 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 bubble formation to obtain a non-roundness. However, it is difficult to set the conditions to reduce the amount by 5% and the reproducibility is poor.
It is not practical because the bubbles are crushed by the shearing stress generated in the pressure-sensitive adhesive during application of the pressure-sensitive adhesive, or the bubbles cannot be uniformly dispersed.

Further, Japanese Patent Laid-Open No. 63-89582 proposes a method of improving the stability of the pressure-sensitive adhesive or bubbles in the adhesive by incorporating hollow glass microspheres having a diameter of 200 μm or less. However, the glass microspheres proposed by the method generally have non-uniform sphere diameters.
Therefore, for example, when the adhesive is applied to a thickness of 100 μm, if glass microspheres with an average particle size of 100 μm are used,
Spheres with a particle size larger than the average particle size will cause clogging at the coating head part, hindering the coatability of the adhesive,
Even when the adhesive surface is not coated with streaky adhesive, so-called dust streaks occur, or even when it is applied together with the adhesive without causing clogging, spheres with a particle size larger than the adhesive thickness are And the smoothness of the adhesive surface is impaired, resulting in poor adhesive properties. Further, in this case, this problem can be solved by using glass microspheres having a small spherical diameter with a maximum spherical diameter of less than 100 μm, but there is a drawback that the effect of improving the stability of bubbles is weakened.

In any case, when a bubble is contained in the pressure-sensitive adhesive or the adhesive, a method for achieving both the improvement of the characteristic of the pressure-sensitive adhesive or the adhesive and the improvement of the stability of the bubble with time with good reproducibility is available. The current situation is that there are none.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bubble-containing hot melt type pressure-sensitive adhesive excellent in removability, low temperature characteristics and adhesion to rough surface. The term "removability" as used herein means that when the adhesive tape is peeled off, there is no phenomenon such as damage to the adherend or cutting of the tape.

[0008]

Means for Solving the Problems The present invention is a bubble-containing hot-melt pressure-sensitive adhesive, wherein the pressure-sensitive adhesive contains 2 to 30% by weight of a solid lumpy inorganic filler having an average particle diameter of 200 μm or less. It is a hot melt adhesive containing.

In the present invention, examples of the solid filler in the form of solid particles used for the purpose of improving the stability of bubbles include calcium carbonate, magnesium carbonate, titanium oxide, talc, etc., but calcium carbonate is preferred. . The average particle size is preferably 200 μm or less, as described below in the section “Action”. The addition amount of the inorganic filler is preferably 2 to 30% by weight in the adhesive. If it is less than 2% by weight, the stability of bubbles in the pressure-sensitive adhesive is poor. Also, 30
When the content is more than 10% by weight, the pressure-sensitive adhesive becomes hard and the adhesiveness to a rough surface and the low temperature characteristics deteriorate.

In the present invention, a foaming agent is used to contain bubbles in the adhesive. Examples of the foaming agent include chemical decomposition type foaming agents that generally generate decomposition gas such as nitrogen, carbon dioxide and water vapor when heated, and specifically, "Uniform" of Otsuka Chemical Co., Ltd., and "Nagawa Kasei Co., Ltd.""Biniform" etc. The bubbles formed by the foaming agent are preferably 5 to 40 vol% of the total volume of the adhesive. If it exceeds 40 vol%, the cohesive force and adhesive force of the pressure-sensitive adhesive will be significantly reduced. On the other hand, when the content is 5 vol% or less, the effect of containing bubbles is poor, so that the adhesion to rough surfaces and the low temperature characteristics are deteriorated, and the removability is deteriorated.

The composition of the hot melt type pressure-sensitive adhesive used in the present invention is not particularly limited, but in general, a pressure-sensitive adhesive using a thermoplastic block copolymer as a main elastomer is used. The block copolymer is generally represented by an AB type or an ABA type, where 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 are AB type styrene-isoprene block copolymers, styrene-butadiene block copolymers, AB-
As A type, styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer, and hydrogenated products thereof, styrene-ethylene-propylene-styrene block copolymer, styrene-
Examples thereof include thermoplastic elastomers such as ethylene-butylene-styrene block copolymers. A tackifier resin, a softening agent, an antiaging agent, and an ultraviolet absorber are blended with these elastomers for use. Examples of the tackifying resin include known ones such as aliphatic petroleum resin, aromatic petroleum resin, rosin resin, terpene resin and coumarone-indene resin. Examples of the softening agent include naphthenic oil, aromatic oil, paraffin oil and the like. Examples of the antioxidant include bisphenol-based and triazine-based antioxidants.

A polyethylene type as an elastomer component,
Known polyolefin-based elastomers such as polypropylene-based and ethylene-vinyl acetate copolymer may be used within a range not exceeding 20% by weight of the total elastomer.

[0013]

By using the solid lump-shaped inorganic filler of the present invention, even when the inorganic filler has a non-uniform particle diameter and a lump having a particle diameter larger than the thickness of the adhesive is mixed, Due to the shearing force, the filler agglomerates are broken within a range not exceeding the coating thickness of the pressure-sensitive adhesive and do not project onto the pressure-sensitive adhesive surface. However, when the particle size of the inorganic filler is much larger than the pressure-sensitive adhesive thickness, the inorganic filler is less likely 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 are projected on the surface of the pressure-sensitive adhesive. Further, generally, the thickness of the adhesive of the 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 of disappearance of air bubbles with the passage of time is that air bubbles move in the pressure-sensitive adhesive and coalesce to enlarge the size of the air-bubbles, which then scatter out of the pressure-sensitive adhesive. This suppresses the movement of bubbles in the pressure-sensitive adhesive and stabilizes the bubbles. Incidentally, JP-A-6
When the hollow glass microspheres shown in JP-A-3-89582 are used, the microspheres break due to the shearing force inside the pressure-sensitive adhesive during application of the pressure-sensitive adhesive to form thin scales, and thus the stability of the bubbles. Is inferior to the filler of the present invention.

[0015]

EXAMPLES The present invention will be specifically described below 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 melt 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) Coumaron indene resin ^{* 3)} 35 parts by weight (D ) Naphthenic oil ^{* 4)} 50 parts by weight (E) 1 part by weight of bisphenol anti-aging agent * 1): Califlex TR1107 (manufactured by Shell Chemical Co., Ltd.) * 2): Quinton D100 (manufactured by Nippon Zeon Co., Ltd.) * 3): Escuron G90 [Nippon Steel Chemical Co., Ltd.] * 4): Shelf Rex 371N [Shell Chemical Co., Ltd.]

To this base adhesive melt, as a solid inorganic filler, calcium carbonate having an average particle size of 50 μm (trade name; cold water # 100, Nitto Koka Kogyo Co., Ltd.) is used per 100 parts by weight of the adhesive. 15 parts by weight (13.0% by weight), and uniform AZ-L as a thermal decomposition type foaming agent
0.5 parts by weight of [Otsuka Chemical Co., Ltd.] was added to 100 parts by weight of the adhesive, and the mixture was stirred and melted to prepare a bubble-containing hot-melt adhesive composition. Bubble-containing hot melt type pressure-sensitive adhesive obtained according to the above, on a hot plate,
It was melt-coated on a polyester film having a thickness of 38 μm so that the thickness of the adhesive was 55 μm.

Example 2 To the base adhesive melt used in Example 1, calcium carbonate having an average particle diameter of 65 μm (trade name; Kansui # 70, Nitto Koka Kogyo Co., Ltd.) was added as a solid inorganic filler. Adhesive 1
15 parts by weight (13.0% by weight) with respect to 00 parts by weight, 0.5 parts by weight of the decomposing foaming agent used in Example 1 with respect to 100 parts by weight of the pressure-sensitive adhesive were added, and the mixture was melt-stirred at 195 ° C. To prepare a bubble-containing hot-melt pressure-sensitive adhesive composition. The bubble-containing hot-melt 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 would have a thickness of 70 μm.

Comparative Example 1 Instead of the inorganic filler used in Example 1, inorganic hollow particles having an average particle size of 49 μm [trade name; Microcells S
L-75, manufactured by Onoda Cement Co., Ltd. was used, and the same operation as in Example 1 was performed.

Comparative Example 2 Instead of the inorganic filler used in Example 2, inorganic hollow particles having an average particle size of 65 μm (trade name: Philite 200)
/ 7, manufactured by Nippon Philite Co., Ltd.] was used, and the same operation as in Example 2 was performed.

Comparative Example 3 In Example 1, 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 tapes obtained in Examples 1 and 2 and Comparative Examples 1 to 3 were tested for pressure-sensitive adhesive thickness after normal aging and after 40 ° C. × 1 month aging. Further, the adhesive strength, removability, low temperature characteristics, and adhesion to rough surface were tested by the following test methods.

Adhesion According to JIS Z0237, a 25 mm width adhesive tape is attached to a stainless steel panel in an atmosphere of 23 ° C., a 2 kg rubber roll is pressure-bonded back and forth once at a speed of 300 mm / min, and a peeling angle after leaving for 20 minutes is 180 degrees. The peeling force was measured at a peeling speed of 300 mm / min.

Removability: Adhesive tape is attached to a decorative plywood in an atmosphere of 23 ° C. and 5 kg
Roll back and forth twice at a speed of 300 mm / min and immediately 1
It was peeled off rapidly at a peeling angle of 80 degrees, and the peeled state of the coated surface of the decorative plywood was observed. Those without peeling of the coating have removability.

Low temperature properties (ball tack value, adhesion to cardboard) As an index of low temperature properties, the ball tack value at 5 ° C and the adhesion to cardboard were tested by the following test methods.

Ball Tack Value J. According to the DOW method, a tilt angle of 3 at 5 ° C.
Stick a 10 cm long adhesive tape on a 0 degree stainless steel plate 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 maximum steel ball stopped on the adhesive tape was defined as the ball tack value. The larger the ball tack value, the higher the initial adhesiveness.

Adhesion to cardboard After leaving the K liner cardboard and the adhesive tape in the atmosphere of 5 ° C. for 1 hour or more, the adhesive tape is attached to the cardboard,
One back-and-forth press-bonding under a load of 850 g was performed, followed by immediate rapid peeling at a peeling angle of 180 degrees, and the degree of paper plucking on the cardboard paper surface was shown as a ratio (%) to the adhesive tape application area.
In addition, the larger the corrugating rate of the corrugated paper, the better the characteristics.

Adhesion to rough surface In a 23 ° C. atmosphere, an adhesive tape having a width of 25 mm is attached to a concrete block, and a 2 kg rubber roll is pressure-bonded back and forth once at a speed of 300 mm / min.
And a peeling force of 300 mm / min was measured.

Test Results Table 1 shows the results obtained by the above tests.

[0030]

[Table 1]

As is clear from Table 1, in Examples 1 and 2, the removability, the low temperature characteristics and the adhesion to rough surface are excellent, the change of the pressure-sensitive adhesive thickness is small, and the stability of bubbles is also good. Is. On the other hand, in Comparative Examples 1 and 2, although the change in thickness was relatively small and the stability of the bubbles was good, hollow particles were projected on the surface of the adhesive, or hollow particles having a particle size larger than the average particle size were formed. However, clogging occurs at the tip of the applicator, causing streak-like dust streaks to which the adhesive is not applied, resulting in poor adhesive properties. Further, in Comparative Example 3 including only the base adhesive containing no filler and air bubbles, there is no removability, and low temperature characteristics and adhesion to rough surfaces are also poor.

[0032]

According to the present invention, even if the particle size of the inorganic filler is non-uniform and a filler having a particle size larger than the adhesive thickness is mixed, the smoothness of the adhesive surface can be maintained. Moreover, it is possible to prevent the bubbles in the adhesive from collapsing or disappearing. The retention of smoothness and the prevention of disappearance of bubbles bring about excellent effects in low-temperature characteristics, adhesion to rough surface and removability of the hot melt adhesive containing bubbles. By applying the bubble-containing hot melt type adhesive according to the present invention to a film, kraft paper, cloth base material or the like, an adhesive tape having excellent properties in applications such as packaging and temporary fixing of building materials can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kinnosuke Hino 2-4, 9danminami, Chiyoda-ku, Tokyo Nichiban Co., Ltd. (72) Kensei Takahashi 2-chome, 9danminami, Chiyoda-ku, Tokyo 2-4 Inside Nichiban Co., Ltd. (72) Inventor Hideyuki Nakajima 2-4 2-9 Kudanminami, Chiyoda-ku, Tokyo Inside Nichiban Co., Ltd.

Claims (1)

[Claims] 1. A bubble-containing hot-melt pressure-sensitive adhesive, comprising 2 to 30% by weight of a solid lump-shaped inorganic filler having an average particle size of 200 μm or less in the pressure-sensitive adhesive.