JP7620636B2 - Adhesive tape and its manufacturing method - Google Patents

Description

The present invention relates to an adhesive tape and a method for manufacturing the same.

Adhesive tapes made by applying an adhesive containing a styrene-based block copolymer and a tackifier to a substrate are used for a variety of purposes.

In addition, nonwoven fabrics are widely used as a base material for tapes because they are porous, have sound-absorbing properties, have excellent mechanical strength, such as tensile strength, and are inexpensive.

JP 2015-203032 A

On the other hand, since nonwoven fabric is porous, and the coating liquid is on the back side of the substrate, it has been considered difficult to apply solvent-based or water-based adhesives directly because of their low viscosity. Therefore, a method of using a relatively high viscosity hot melt adhesive and applying it directly to the substrate has been considered.
However, when a hot melt adhesive is applied to a porous substrate with large irregularities, such as a nonwoven fabric, the adhesive does not run through to the back of the substrate, but the adhesive-coated surface becomes uneven, reducing the contact area of the adhesive with the adherend, resulting in the problem of insufficient adhesive strength and holding power.
To solve this problem, for example, it is possible to increase the thickness of the adhesive, but to obtain the required adhesive properties, it is necessary to apply more than twice the amount of adhesive, which is inefficient. Furthermore, the weight of the tape itself becomes heavy, making it difficult to handle. To solve this problem, it is necessary to make the adhesive itself strong and with high holding power so that the required adhesive properties can be obtained even if the contact area of the adhesive is small.
The stronger the adhesive strength, the better the adhesive will adhere to the adherend, but if the adhesive strength is too strong, it will be difficult to unwind the substrate when wound into a tape.
In order to reduce the unwinding force, a release agent can be applied to the back surface of the substrate; however, in order to apply a release agent to a porous substrate such as a nonwoven fabric, a release agent solution in which the release agent is dissolved in an organic solvent such as toluene must be applied. Since the viscosity of the solution is low, there is a problem of the release agent getting onto the back surface of the substrate, similar to the case where the pressure sensitive adhesive is applied.
Therefore, there is a need for a pressure-sensitive adhesive that does not require a release agent, has strong adhesive strength that allows it to adhere well to an adherend, and has high holding power.

The present invention has been made in consideration of such problems, and provides an adhesive tape that uses nonwoven fabric and has strong adhesive strength and high holding power on adherends.

According to the present invention, there is provided an adhesive tape comprising a substrate and an adhesive layer provided on the substrate, the substrate being a nonwoven fabric, the adhesive layer containing an adhesive, the adhesive containing a styrene-isoprene-styrene block copolymer and a tackifier, the tackifier having a softening point of 100°C or higher in the JIS K2207 6.4 softening point test method (ring and ball method), the styrene-isoprene-styrene block copolymer having a styrene content of 14 to 30% by mass, a coupling rate of 30 to 90% by mass, and a mass ratio of the tackifier to the styrene-isoprene-styrene block copolymer of 0.5 to 1.5.

After extensive research, the inventors discovered that even when a nonwoven fabric is used as the substrate, an adhesive tape with strong adhesive strength and high retention power can be obtained by using an adhesive containing an appropriate ratio of a styrene-isoprene-styrene block copolymer having a specified composition and a tackifier having specified thermal properties, which led to the completion of the present invention.

Various embodiments of the present invention will be described below. The embodiments described below can be combined with each other.
Preferably, in the pressure-sensitive adhesive tape, the tackifier is at least one selected from the group consisting of C5 petroleum resin, C9 petroleum resin, C5C9 petroleum resin, hydrogenated C9 petroleum resin, alicyclic petroleum resin, alicyclic/aromatic petroleum resin, terpene resin, rosin resin, rosin ester resin, terpene phenol resin, and alkylphenol resin.
Preferably, the adhesive tape contains 5 to 25 parts by mass of a plasticizer based on 100 parts by mass of the styrene-isoprene-styrene block copolymer, and the plasticizer is DINA.
Preferably, the adhesive tape has a styrene content of 16 to 20% by mass.
Preferably, the pressure-sensitive adhesive tape has a coupling rate of 40 to 85% by mass.
Preferably, the adhesive tape has an adhesive strength of 1.5 N/cm or more according to JIS Z0237 10. Adhesive strength, and a holding strength of 10 minutes or more according to JIS Z0237 13. Holding strength.

According to another aspect, a method for manufacturing the above-mentioned adhesive tape is provided, which includes a step of applying the adhesive onto the substrate by a non-contact coating method.

The following describes an embodiment of the present invention. The various features shown in the following embodiment can be combined with each other. In addition, each feature can be an invention independently.

1. Adhesive Tape An adhesive tape according to one embodiment of the present invention comprises a substrate and an adhesive layer provided on the substrate. The substrate is a nonwoven fabric, and the adhesive layer contains an adhesive. In one aspect, the adhesive tape preferably does not have a release agent layer. The adhesive tape may have an adhesive layer provided on one surface of the substrate and a release agent layer on the other surface (back surface of the substrate); however, the nonwoven fabric substrate has large irregularities, and the wound tape can be pulled out without providing a release agent layer.

1-1. Substrate The substrate is preferably a nonwoven fabric having a stitch-bond or spun-bond structure.
The nonwoven fabric is preferably used because it has a cut surface that is not easily frayed and has the strength and flexibility required for an adhesive tape substrate. The spunbond nonwoven fabric has a hand-tearable substrate, so when used as an adhesive tape substrate, it can be cut by hand without using tools such as scissors. In addition, the spunbond nonwoven fabric has a relatively fine mesh among various nonwoven fabrics, so it is preferably used because it is less likely to soak in when an adhesive is applied.
The nonwoven fabric may be made of any of the conventionally known materials, such as cellulose, glass, polyamide, polyethylene, polyester, polypropylene, polyurethane, and rayon.
The basis weight of the substrate is preferably 30 to 150 g/ ^m2 , more preferably 50 to 110 g/ ^m2 . If it is smaller than this range, the strength of the substrate is too weak, and the substrate is stretched or broken by a small force, which is inconvenient. If it is larger than this range, the substrate becomes hard and loses flexibility, which is not preferable because it does not fit well with the adherend.
1-2. Adhesive <Styrene-isoprene-styrene block copolymer>
The pressure-sensitive adhesive contains a styrene-isoprene-styrene block copolymer (SIS copolymer) as a styrene-based block copolymer, and a tackifier. The pressure-sensitive adhesive may contain a styrene-butadiene block copolymer (SBS copolymer or SBBS copolymer) as the styrene-based block copolymer within a range that does not impair the effects of the present invention, but when a styrene-butadiene block copolymer is used, the adhesive may become hard and have poor processability. Therefore, the pressure-sensitive adhesive preferably does not substantially contain a styrene-butadiene block copolymer as a styrene-based block copolymer, and more preferably contains only an SIS copolymer as a styrene-based block copolymer.

The mass ratio of tackifier to SIS copolymer, i.e. (parts by mass of tackifier)/(parts by mass of SIS copolymer), is 0.5 to 1.5, and preferably 0.6 to 1.2. By setting it in this range, strong adhesive strength and high retention power can be obtained. Specific examples of the mass are 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, and 1.5, and may be within a range between any two of the numerical values exemplified here.

The SIS copolymer is a block copolymer having a polystyrene block and a polyisoprene block. The SIS copolymer includes a styrene-isoprene-styrene triblock copolymer and a styrene-isoprene diblock copolymer, and the coupling rate in the SIS copolymer is 30 to 90% by mass, preferably 40 to 85% by mass, and more preferably 40 to 50% by mass. By setting the coupling rate in this range, the adhesive can be easily attached to the adherend (back surface of the substrate) and can be easily applied with the adhesive. The coupling rate is specifically, for example, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, or 85%, and may be within a range between any two of the values exemplified here.

The coupling rate (%) can be calculated by 100 x (parts by mass of triblock copolymer) / (parts by mass of diblock copolymer + part by mass of triblock copolymer). Specifically, the coupling rate can be calculated by measuring the molecular weight of the SIS copolymer by gel permeation chromatography (GPC) and calculating it from the area ratio of the peak attributable to the diblock copolymer and the peak attributable to the triblock copolymer in the obtained chart. There are no particular limitations on the method for changing the coupling rate, but examples include blending two or more SIS copolymers with different coupling rates, such as changing the ratio of the amount of coupling agent/the amount of initiator used during polymerization.

The weight average molecular weight of the triblock copolymer is not particularly limited, but is, for example, 120,000 to 1,200,000, preferably 140,000 to 1,000,000, and more preferably 160,000 to 800,000. The weight average molecular weight of the diblock copolymer is not particularly limited, but is, for example, 60,000 to 250,000, preferably 70,000 to 230,000, and more preferably 80,000 to 220,000. The weight average molecular weight of the diblock copolymer is preferably smaller than the weight average molecular weight of the triblock copolymer. The weight average molecular weight can be determined by gel permeation chromatography (GPC).

The styrene content of the SIS copolymer is 14 to 30% by mass, preferably 16 to 20% by mass. By setting the styrene content in this range, the adhesive can be easily attached to the adherend (back surface of the substrate) even when the substrate is a nonwoven fabric with large irregularities, and can also be easily coated with an adhesive. Specific examples of the styrene content are 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, and 30% by mass, and may be within a range between any two of the values exemplified here.

Styrene content can be measured using the method described in JIS K6383. The method for changing the styrene content is not particularly limited, but examples include a method of changing the styrene/isoprene ratio of the monomer to obtain an SIS copolymer having the desired styrene content by living anionic polymerization, and a method of blending two or more types of SIS having different styrene contents to obtain an SIS copolymer having the desired styrene content.

The SIS copolymer is preferably a linear type. It may have better retention power than the radial type. A linear SIS copolymer is a straight-chain linear SIS copolymer.

<Tackifier>
The tackifier is a tackifier having a softening point of 100°C or higher according to JIS K2207 6.4 softening point test method (ring and ball method). The softening point is preferably 100 to 133°C, more preferably 100 to 125°C. By using a tackifier having a softening point of 100°C or higher, the adhesive is more likely to maintain its cohesive force and has excellent holding power. The softening point is specifically, for example, 100, 105, 110, 115, 120, 125, 130, or 133°C, and may be within a range between any two of the values exemplified here.

The tackifier is, for example, at least one selected from the group consisting of C5 petroleum resin, C9 petroleum resin, C5C9 petroleum resin, hydrogenated C9 petroleum resin, alicyclic petroleum resin, alicyclic/aromatic petroleum resin, terpene resin, rosin resin, rosin ester resin, terpene phenol resin, alkylphenol resin, etc. The tackifier is preferably C5 petroleum resin obtained by polymerizing dicyclopentadiene, or C5C9 petroleum resin, or hydrogenated C9 petroleum resin, from the viewpoint of obtaining strong adhesive strength.

<Plasticizer>
The adhesive according to one embodiment of the present invention preferably contains a plasticizer. The adhesive contains preferably 5 to 25 parts by mass, more preferably 5 to 20 parts by mass, of the plasticizer relative to 100 parts by mass of the styrene-isoprene-styrene block copolymer. By setting the amount in this range, the adhesive is excellent in ease of attachment to the adherend (back surface of the substrate) and ease of application of the adhesive. The amount of the plasticizer in the adhesive is, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 parts by mass relative to 100 parts by mass of the styrene-isoprene-styrene block copolymer, and may be within a range between any two of the numerical values exemplified here.

As for the plasticizer, phthalate-based plasticizers are preferred because they are compatible with styrene-isoprene-styrene block copolymers and can achieve plasticizing effects with a small amount. Examples of phthalate-based plasticizers include DINA (diisononyl adipate), DEHP (di-(2-ethylhexyl) phthalate), DBP (dibutyl phthalate), BBP (butyl benzyl phthalate), DINP (diisononyl phthalate), DIDP (diisodecyl phthalate), and DNOP (di-normal octyl phthalate). However, phthalate esters other than DINA may be subject to regulations such as REACH (Registration, Evaluation, Authorization, and Restriction of Chemicals), so caution is required when using them, but DINA is not subject to these regulations and can be used preferably. Furthermore, even if a sample of DINA with an adhesive tape attached to an adherend is left in a high-temperature atmosphere, the plasticizer does not easily bleed out and does not easily contaminate the adherend.

<Other additives>
The pressure-sensitive adhesive may contain various additives such as inorganic fillers, modifiers, stabilizers, antioxidants, and ultraviolet absorbers, as necessary, within the range that does not impair the effects of the present invention.

1-2. Pressure-sensitive adhesive layer The basis weight of the pressure-sensitive adhesive layer is not particularly limited, but is, for example, 10 to 100 g/m ^2. If the basis weight is too low, the adhesion becomes insufficient, and if it is too high, the coating performance may deteriorate.

1-3. Characteristics of the adhesive tape The adhesive tape preferably has an adhesive strength of 1.5 N/cm or more as specified in JIS Z0237 10. Adhesive strength. The adhesive tape preferably has a holding strength of 10 minutes or more as specified in JIS Z0237 13. Holding strength. By setting the value in this range, the tape has high holding strength while being easy to handle when wound into a tape shape.

2. Method for Producing Adhesive Tape A method for producing an adhesive tape according to one embodiment of the present invention includes a step of applying the above-described adhesive onto a substrate.

There are no particular limitations to the coating method, but it is preferable to heat, melt, and knead the adhesive raw materials and apply them using the hot melt method, and it is even more preferable to apply them using a non-contact coating method. This method may have better holding power than the contact method.

Examples of hot melt contact coating include slot die coating and roll coating.

An example of non-contact coating is a cross coater (manufactured by ITW Dynatech). Generally, when an adhesive is applied directly to a substrate such as a nonwoven fabric, the adhesive soaks into the substrate, resulting in a significant decrease in adhesive properties. Using a cross coater is preferable because it prevents the adhesive from soaking into the nonwoven fabric, making it less likely to cause a decrease in adhesive properties.

The present invention will be described in more detail below with reference to examples. Note that these examples are merely illustrative and do not limit the scope of the present invention.

<Preparation of adhesive tape>
Adhesive tapes were prepared under the conditions described in Tables 1 to 3. An adhesive tape for evaluation was prepared by coating the adhesive on the substrate with a non-contact coating method so that the adhesive was applied to a basis weight of 60 g/ ^m2 to form an adhesive layer. As the adhesive, a tackifier, a plasticizer (DINA, Monosizer W242 manufactured by DIC Corporation), an antioxidant (Irganox 1726 manufactured by BASF), and an ultraviolet absorber (JF-77P manufactured by Johoku Chemical Industry Co., Ltd.) were added to 100 copolymers, and the mixture was kneaded at 150°C to obtain an adhesive in a molten state, which was then coated with a cross coater to obtain an adhesive layer. The stitch-bonded nonwoven fabric and spun-bonded nonwoven fabric are porous substrates, and the OPP film, PE woven fabric + PE laminate, and PET woven fabric + PE laminate are non-porous substrates.

The components in Tables 1 to 3 are as follows.
SIS: A. Quintac 3433N manufactured by Zeon Corporation
(styrene content 16% by mass, coupling rate 44% by mass)
B. Quintac 3190 manufactured by Zeon Corporation
(styrene content 30% by mass, coupling rate 40% by mass)
C. Quintac 3520 manufactured by Zeon Corporation
(styrene content 15% by mass, coupling rate 78% by mass)
D. Quintac 3270 manufactured by Zeon Corporation
(styrene content 24% by mass, coupling rate 33% by mass)
E. Quintac 3421 manufactured by Zeon Corporation
(styrene content 14% by mass, coupling rate 74% by mass)
F. Quintac 3390 manufactured by Zeon Corporation
(styrene content 48% by mass)
G. Quintac 3520 manufactured by Zeon Corporation
(styrene content 15% by mass, coupling rate 22% by mass)
H. SIS5002 manufactured by JSR Corporation
(styrene content 22% by mass, coupling ratio 85% by mass)
I. Berlin China Petrochemical YH1105
(styrene content 15% by mass, coupling rate 99% by mass or more)
SBS: Kraton Corporation Kraton D1152
C5 petroleum resin: Quinton R100 manufactured by Zeon Corporation
C5C9 petroleum resin: Quinton S195 manufactured by Zeon Corporation
Hydrogenated C9 petroleum resin: Arcon P-100 manufactured by Arakawa Chemical Industries, Ltd.
Terpene: YS Resin PX1250 manufactured by Yasuhara Chemical Co., Ltd.
Terpene phenol: SUMILITE RESIN PR-12603 manufactured by Sumitomo Bakelite Co., Ltd.
Rosin ester: Haritac FK125 manufactured by Harima Chemical Group Co., Ltd.

<Rewinding adhesive tape>
Regarding the rewinding of the adhesive tape, the substrate coated with the adhesive was wound around a paper tube with a diameter of 3 inches, and then cut to a width of 20 mm to obtain an adhesive tape roll. The adhesive tape roll was measured for its low speed rewind force according to JIS Z0237 11. It was determined whether the tape substrate could be pulled out by hand. The results are shown in Tables 1 to 3.
◯: The unwinding force was 3.0 N/cm or less, so the tape substrate could be pulled out.
×: The unwinding force exceeded 3.0 N/cm, making it difficult to pull out the tape substrate.

<Ease of adhesion to adherend (back surface of substrate)>
Regarding the ease of adhesion to the adherend (back of the substrate), two pieces of the substrate coated with the adhesive were cut into a size of 20 mm wide x 140 mm long, and one piece was attached to a SUS plate. The other piece was attached to the back of the substrate from above, and pressed once with a roller of mass 2 kg. After 1 minute, the substrate attached on top was peeled off at an angle of 180°, and the ease of adhesion to the adherend was judged based on the peeling force at that time. The measurement was performed in an environment of room temperature 23°C ± 2°C, and the pulling speed was 500 mm/min.
The results are shown in Tables 1 to 3.
A: The peeling force was 1.5 N/cm or more.
Δ: The peeling force was 1.0 N/cm or more and less than 1.5 N/cm.
×: The peeling force was less than 1.0 N/cm.

<Ease of applying adhesive>
The ease of application of the adhesive was evaluated by extruding the adhesive from the coating head of the coating equipment and applying it to a substrate, and judging whether streaks of the adhesive were observed. The samples observed were adhesive-coated substrates with a width of 300 mm and a length of 1 m. The results are shown in Tables 1 to 3.
A: The area of the adhesive streaks on the adhesive coated surface was less than 5%.
Δ: The area of the adhesive streaks on the adhesive coated surface was 5 to 30%.
×: The area of adhesive streaks on the adhesive coated surface exceeded 30%.

<SUS adhesion>
The 180° peel adhesive strength to a SUS plate was measured according to JIS Z0237 "10. Adhesive strength". The results are shown in Tables 1 to 3.

<Holding power>
Measurement was performed according to JIS Z0237 "13. Holding power". The adherend was a SUS plate, and the adhesive tape was applied to an area of 20 mm x 20 mm. The measurement temperature was 60°C, the load was 1 kg, and the time until the weight fell was measured. The results are shown in Tables 1 to 3.

Claims (7)

A substrate and a pressure-sensitive adhesive layer provided on the substrate,
The substrate is a nonwoven fabric,
The pressure-sensitive adhesive layer includes a pressure-sensitive adhesive,
The pressure-sensitive adhesive contains a styrene-isoprene-styrene block copolymer and a tackifier,
The tackifier has a softening point of 100° C. or higher according to JIS K2207 6.4 softening point test method (ring and ball method),
The styrene-isoprene-styrene block copolymer is
The styrene content is 14 to 30% by mass,
The coupling ratio is 30 to 60% by mass,
a mass ratio of the tackifier to the styrene-isoprene-styrene block copolymer is 0.5 to 1.5;
The pressure-sensitive adhesive contains 5 to 20 parts by mass of a plasticizer based on 100 parts by mass of the styrene-isoprene-styrene block copolymer,
The plasticizer is a phthalate ester plasticizer .
Adhesive tape (excluding those equipped with aluminum foil). The adhesive tape according to claim 1, wherein the tackifier is at least one selected from the group consisting of C5 petroleum resin, C9 petroleum resin, C5C9 petroleum resin, hydrogenated C9 petroleum resin, alicyclic petroleum resin, alicyclic/aromatic petroleum resin, terpene resin, rosin resin, rosin ester resin, terpene phenol resin, and alkylphenol resin. The adhesive tape according to any one of claims 1 to 2, wherein the plasticizer is DINA. The adhesive tape according to any one of claims 1 to 3, wherein the styrene content is 16 to 20% by mass. The pressure-sensitive adhesive tape according to any one of claims 1 to 4, wherein the coupling ratio is 40 to 60 mass %. JIS Z 0237 10. The adhesive strength is 1.5 N/cm or more,
JIS Z 0237 13. Holding power is 10 minutes or more.
The adhesive tape according to any one of claims 1 to 5. A method for producing the adhesive tape according to any one of claims 1 to 6, comprising the steps of:
The pressure-sensitive adhesive is applied to the substrate by a non-contact coating method.
A method for manufacturing adhesive tape.