JPH06346039A - Pressure-sensitive adhesive composition excellent in low-temperature tack and pressure-sensitive adhesive tape prepared by using same - Google Patents

Abstract

PURPOSE: To obtain an aq. emulsion self-adhesive compsn. excellent in low temp. tackiness and having sufficient flocculation force at the same time and generating no paste residue, and to prepare a self-adhesive tape using the same.

CONSTITUTION: An aq. emulsion self-adhesive compsn. contains a polymer (A) obtained by the polymn. of a monomer containing 100 pts.wt. of an acrylate monomer (1) and 0.1-5 pts.wt. of a carbonyl group-containing monomer (2) and having a glass transition point of -75 to -45°C and storage elastic modulus of 1×10⁵-4×10⁶ dyn/cm² and a polyfunctional hydrazide compd. (B) the amt. of which is 0.02-0.5 mol per 1 mol of the carbonyl group in the carbonyl group- containing monomer (2).

COPYRIGHT: (C)1994,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous emulsion pressure-sensitive adhesive composition excellent in low-temperature tackiness and a pressure-sensitive adhesive tape using the same.

[0002]

2. Description of the Related Art An adhesive having excellent tackiness at low temperature and having sufficient cohesive force and holding power is required in the field of adhesive tape, particularly in a masking tape used for working in extremely cold regions. . Natural rubber adhesives have been used for many years to satisfy this requirement, but they have drawbacks such as poor weather resistance and the need to use a solvent system for coating. .

For this reason, acrylic adhesives have come to be used as a substitute for natural rubber adhesives. However, in the acrylic pressure-sensitive adhesive, there is a problem that the glass transition temperature and the storage elastic modulus are increased and the low-temperature tackiness is deteriorated if sufficient crosslinking is performed to enhance the cohesive force and the holding force of the pressure-sensitive adhesive. It was That is, there was no acrylic pressure-sensitive adhesive having both sufficient cohesive strength and holding power and sufficient low-temperature tackiness.

Therefore, in Japanese Patent Laid-Open No. 59-226078,
A pressure-sensitive adhesive composition having good adhesion to a polyolefin surface is disclosed. This composition comprises (a) an acrylate monomer 5 having an alkyl group having 4 to 8 carbon atoms.
0-99% by weight, (b) acrylate monomer having an alkyl group having 1 to 3 carbon atoms, methacrylate monomer having an alkyl group having 1 to 3 carbon atoms, vinyl ester of carboxylic acid, acrylo (methacrylo) nitrile , 0-50% by weight of either styrene or tertiary butyl acrylate,

(C) 0.5 to 5 of monoolefinic acid unsaturated monomer having 3 to 5 carbon atoms, dicarboxylic acid, amide compound or hydroxy acrylate having 2 to 5 carbon atoms in the alkyl moiety. %, And (d) a carbonyl group-containing monomer in an amount of 0.5 to 5% by weight, the polymer having a glass transition temperature of 0 ° C. or lower and 40 to 70% in the form of an aqueous dispersion. The water-soluble hydrazine compound is contained in an amount of 0.05 to 2 mol with respect to 1 mol of the carbonyl group of the carbonyl group-containing monomer (d). Specifically, the glass transition temperature of the polymer is -10 ° C to -40 ° C. Low temperature tackiness,
Although the cohesive strength and tackiness are not described, this tackiness agent composition actually has poor low temperature tackiness (0 ° C).
The ball tack is less than 5).

Further, JP-A-54-110248 and JP-A-54-144432 disclose coating materials and pressure-sensitive adhesives having compositions similar to the above. However, although nothing is described about low-temperature tackiness, cohesive strength, and tackiness, it actually has a drawback of low low-temperature tackiness (ball tack 5 or less at 0 ° C.).

[0007]

Therefore, the present invention is to provide an aqueous emulsion pressure-sensitive adhesive composition excellent in low-temperature tackiness and having sufficient cohesive force, and a pressure-sensitive adhesive tape using the same.

[0008]

In order to solve the above-mentioned problems, the present invention provides an aqueous emulsion pressure-sensitive adhesive composition comprising (A) (1) 100 parts by weight of an acrylate monomer and (2) a carbonyl group-containing monomer: A polymer obtained by polymerizing a monomer comprising 1 to 5 parts by weight, having a glass transition point of −75 ° C. to −45 ° C. and 1 × 10 ⁵
A polymer having a storage modulus of ~ 4 x 10 ⁶ dyn / cm ² .
And (B) a pressure-sensitive adhesive composition comprising the polyfunctional hydrazide compound in an amount of 0.02 to 0.5 mol per 1 mol of the carbonyl group in the carbonyl group-containing monomer of (2) above; There is provided an adhesive tape comprising the above-mentioned water-based emulsion adhesive composition laminated on a substrate.

[0009]

Specific Description Next, the present invention will be specifically described. Acrylate Monomer The main component of the pressure-sensitive adhesive component of the present invention is an acrylic polymer composed of an acrylate monomer. This is because the acrylic polymer is generally excellent in tackiness at low temperatures, has advantages such as easy polymerization and low cost. The reason why the monomer is defined as an acrylate type here is that it generally has a low Tg and is suitable for this application.

In the present invention, the alkyl group of the acrylate monomer preferably has 5 to 9 carbon atoms, more preferably 8 or 9 carbon atoms. The acrylate monomers having an alkyl group having 5 to 9 carbon atoms are preferable because they have a low Tg of the polymerized polymer among the acrylate monomers, and the Tg of the pressure-sensitive adhesive as defined in the present invention is-. This is because it is easy to control at 45 ° C or lower. Further, an acrylate monomer having an alkyl group having 8 or 9 carbon atoms is preferable because such an acrylate monomer is easy to control the Tg of the pressure-sensitive adhesive as defined in the present invention at −45 ° C. or less and is stored. This is because the elastic modulus can be easily controlled within the range specified in the present invention.

Specific examples of the acrylate monomer used in the present invention include heptyl acrylate, hexyl acrylate, isooctyl acrylate and n-.
Examples thereof include octyl acrylate, 2-ethylhexyl acrylate and isononyl acrylate, with the latter four being particularly preferable. Carbonyl group-containing monomer The carbonyl group-containing monomer is an additive for participating in the crosslinking reaction of the acrylic polymer. The carbonyl group-containing monomer in the present invention is defined as a monomer having at least one carbonyl group other than the carbonyl groups of ester, amide and carboxylic acid and a polymerizable double bond in the molecule.

Examples of the carbonyl group-containing monomer include compounds having an aldehyde or ketone carbonyl group, and specific examples thereof include acrolein, vinyl methyl ketone, vinyl ethyl ketone, vinyl isobutyl ketone, diacetone acrylamide, diacetone methacryl. Examples thereof include amide, formyl styrene, diacetone acrylate, acetonyl acrylate, diacetone methacrylate, 2-hydroxypropyl acrylate-acetyl acetate, butanediol-1,4-acrylate-acetyl acetate.

A preferable amount of the carbonyl group-containing monomer added to the acrylic monomer is acrylic monomer 1
It is 0.1 to 5 parts by weight with respect to 00 parts by weight. If the amount of the carbonyl group-containing monomer is less than 0.1 parts by weight, the crosslinking reaction will be insufficient, and thus the cohesive force will be insufficient and so-called adhesive residue will easily occur. On the other hand, if it exceeds 5 parts by weight, the storage elastic modulus becomes excessive and the tackiness deteriorates.

As an optional component for increasing the polymerization stability and mechanical stability of the p-sodium styrenesulfonate emulsion pressure-sensitive adhesive, sodium p-styrenesulfonate is added in addition to the above-mentioned monomer components before the polymerization of the acrylic polymer. Can be added. The amount of addition is 0.1-1.
This is because 5 parts by weight is preferable, and if it is less than 0.1 part by weight, a sufficient addition effect cannot be obtained, and if it exceeds 1.5 parts by weight, tackiness is deteriorated.

Polymerization of the Polymer The above-mentioned monomer components, namely the acrylate monomer and the carbonyl group-containing monomer, are optionally combined with sodium p-styrene sulfonate as an optional component.
Polymerization is carried out by a conventional emulsion polymerization method. In this case, the reaction medium is 50 to 100 parts by weight of the monomer mixture.
240 parts by weight of water are used. To emulsify the monomer in water, a conventional emulsifier such as sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether nitrate, etc. is added.

This additive is preferably used in an amount of 0.2 to 5 parts by weight based on 100 parts by weight of the monomer mixture. Further, a conventional polymerization initiator such as ammonium persulfate or potassium persulfate is added as a polymerization initiator. The amount is 0.01 to 1 part by weight based on 100 parts by weight of the monomer mixture. The polymerization is preferably carried out at 50 ° C. to 75 ° C. for 1 to 24 hours under an atmosphere of an inert gas such as nitrogen gas. Further, redox initiators such as hydrogen peroxide, divalent iron salt, persulfate, and acidic sodium sulfite are used,
Using the above amount, the reaction is carried out at 5 ° C to 50 ° C for 1 to 24 hours.

[0017]polymer The polymer of the present invention obtained as described above is -75.
Glass transition temperature of ℃ to -45 ℃, and 0 ℃, 1rad / se
Storage elastic modulus under conditions of 1 × 10^Five~ 4 x 10 ⁶dyn / cm
²It is characterized by having. Poly for conventional adhesives
The mer is described in JP-A-59-226078.
As shown in FIG.
Mar was being used. However, for the purposes of the present invention
Conventional glass transition temperature to achieve a certain low temperature tack
Is not appropriate. Low when the glass transition temperature is higher than -45 ° C
Poor in warm tack, prefer ball tack 6 or above at 0 ℃
It does not satisfy the condition of 8 or more. Glass transition
If the temperature is lower than −75 ° C., the cohesive force may decrease too much.
Because there is. Therefore, it has sufficient tackiness and low temperature at low temperature.
In order to obtain an adhesive that has sufficient cohesive strength,
The glass transition temperature of the mer component is in the range of -75 ° C to -45 ° C.
Need to

Here, the glass transition temperature is a loss tangent curve which is a ratio (tan δ) of a storage elastic modulus to a loss elastic modulus obtained by measuring a dynamic viscoelastic behavior in a compression mode using a viscoelasticity spectrometer. It is defined as the temperature showing the maximum point. As the viscoelasticity spectrometer, for example, RSAII viscoelasticity spectrometer manufactured by Rheometrics can be used.

The acrylic polymer used in the pressure-sensitive adhesive of the present invention is 1 × 10 ⁵ to 4 × under the conditions of 0 ° C. and 1 rad / sec.
It has a storage modulus of 10 ⁶ dyn / cm ² . Conventionally, it has been generally tried to control the tackiness by adjusting the glass transition temperature, but the present inventors have found that even at the same glass transition temperature, the tackiness is significantly different due to the difference in storage elastic modulus. The present invention has been completed by specifying the storage elastic modulus range. When the storage elastic modulus is less than 1 × 10 ⁵ dyn / cm ² , the cohesive force is reduced, while when it exceeds 4 × 10 ⁶ dyn / cm ² , the tack property is significantly reduced.

The storage elastic modulus is determined by measuring the dynamic viscoelastic behavior in a compression mode using a viscoelastic spectrometer,
It is defined as the storage modulus at 0 ° C. In this case, as the viscoelasticity spectrometer, for example, RSAII viscoelasticity spectrometer manufactured by Rheometrics can be used. The dynamic viscoelastic behavior was measured by molding a test adhesive into a cylinder with a diameter of 5 mm and a thickness of 7 mm, mounting it on a parallel plate jig, and applying compressive strain at a frequency of 1 rad / sec from -80 ° C. It is performed by applying a temperature change of 150 ° C. and measuring the temperature dependence of the elastic modulus.

The molecular weight of the polymers of the invention is preferably
The weight average molecular weight is 10,000 to 5,000,000. This is because if it is less than 10,000, the cohesive force tends to decrease, and if it exceeds 5 million, polymerization becomes difficult.

Polyfunctional hydrazide compound The pressure-sensitive adhesive composition of the present invention comprises the acrylic polymer (A)
And a polyfunctional hydrazide compound (B). This polyfunctional hydrazide compound (B) crosslinks the acrylic polymer by reacting with the carbonyl group of the carbonyl group-containing monomer (A) (2) incorporated into the acrylic polymer as a copolymerization monomer component. Since this reaction is a dehydration condensation reaction, no reaction occurs in the water-based emulsion, and the reaction occurs rapidly by removing water. Therefore, this polyfunctional hydrazide compound is advantageous for the storage stability of the aqueous emulsion.

The amount of the polyfunctional hydrazide compound added is 0.02 to 0.5 mol with respect to 1 mol of the carbonyl group of the carbonyl group-containing monomer. If it is less than 0.02 mol, crosslinking is insufficient and sufficient cohesive force and holding power cannot be obtained, and adhesive residue is apt to occur when the pressure-sensitive adhesive tape is used. On the other hand, if it exceeds 0.5 mol, the crosslinking becomes excessive and the tackiness deteriorates.

Specific examples of the polyfunctional hydrazide compound include oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, maleic acid dihydrazide, sebacic acid dihydrazide, fumaric acid dihydrazide and the like. The aqueous emulsion pressure-sensitive adhesive composition of the present invention is produced by adding a predetermined amount of the polyfunctional hydrazide compound to the acrylic polymer emulsion polymerization product.

The present invention also relates to a pressure-sensitive adhesive tape obtained by coating the above-mentioned aqueous emulsion pressure-sensitive adhesive composition on a substrate. Examples of the substrate include paper, polyester resin, polypropylene resin, polyimide resin, polyamide resin, vinyl chloride resin, film such as cellophane, woven cloth, non-woven cloth or metal, and ceramic resin. Further, processing such as peeling processing or embossing processing may be performed. Material thickness is 10
-100 μm is suitable. If it is less than 10 μm, the mechanical strength will be poor, and if it exceeds 100 μm, the price will be high.
This is because the tape product becomes thicker.

A suitable coating amount is 5 to 80 g / m ² .
If it is less than 5 g / m ² , an appropriate adhesive force cannot be obtained, and 80 g / m ²
If it exceeds m ² , problems such as sticking out of the adhesive from the edge of the tape occur. The coating can be carried out on one or both sides of the various substrates by ordinary means such as spraying, knife, roll, casting, rolling, or impregnation, and indirect coating, for example, transfer method using silicone-treated paper together. Is also possible.

After applying the adhesive, the applied substrate is dried by a conventional method. For example, it is coated on a PET film with a knife coater, and the coated film is dried in a drying oven at 100 to 120 ° C. for 3 minutes.

[0028]

EXAMPLES Next, the present invention will be described more specifically by way of Examples and Comparative Examples. 2- as an acrylate monomer
Ethylhexyl acrylate (2-EHA), isooctyl acrylate (IOA), isononyl acrylate (INA), butyl acrylate (BA) or ethyl acrylate (EA) is used, and diacetone acrylamide (DAACM) or acrolein is used as a carbonyl group-containing monomer. (Ac) and optionally sodium p-styrene sulfonate (NaSS).

Mixtures of these monomers were prepared using these components in the amounts shown in Tables 1 to 3 and the mixture 10
To 138 parts by weight of water to 0 parts by weight, add 2 parts by weight of sodium dodecyl sulfate as an emulsifier and emulsify,
After that, 0.2 part by weight of ammonium persulfate was added as a polymerization initiator to start the polymerization, and the reaction was completed in 3 hours under a nitrogen gas atmosphere to obtain an aqueous emulsion.

Adipic acid dihydrazide (ADH) or malonic acid dihydrazide (MDH) as a polyfunctional hydrazide compound was added to this emulsion in the amounts shown in Tables 1 to 3 to obtain an aqueous emulsion pressure-sensitive adhesive composition of the present invention. . The adhesive composition was applied onto a PET (polyethylene terephthalate) tape base material having a thickness of 50 μm by a knife coater so that the coating amount after drying was about 30 g / m ^2, and the film was dried at 100 ° C. 120 ° C
And dried for 3 minutes to obtain an adhesive tape of the present invention.

The performance test of the adhesive tape was performed as follows. In accordance with the ball tack test JIS-Z-0237, the adhesive tape (length 100 mm, width 25 mm) is inclined at 30 ° C. at an ambient temperature of 0 ° C., and the steel from the position where the non-adhesive runway is 100 mm. The tackiness was expressed by the maximum diameter of the steel ball that rolls and stops the ball (the diameter of the steel ball is 2 to 32/32 inches, which is 32 times the numerical value).

Creep test According to JIS-Z-0237, the adhesive tape was attached to a stainless steel plate by reciprocating 3 times with a 2 kg roller so that the adhesive area was 12 mm in width and 25 mm in length, and a load of 1 kg was applied thereto. The weight was fixed to the lower end of the tape and hung at an ambient temperature of 25 ° C., and the time until the adhesive tape dropped was measured.

2.5 hours or longer was OK, and less than 2.5 hours was NG. Adhesive tape for measuring adhesive residue (width 25 mm, length 100 mm) 2 kg on glass plate
The tape was reciprocated 3 times with the roller of No. 3, and put in an oven at 65 ° C. for 24 hours and then peeled off, and the presence or absence of adhesive residue was visually observed. The one with adhesive residue was NG, and the one without adhesive residue was OK. The results are shown in Tables 1 to 3 below.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

Next, in order to investigate the effect of adding the crosslinking agent, 100 parts by weight of 2-ethylhexyl acrylate (2-EHA) as an acrylate monomer and diacetone acrylamide (DAACM) as a carbonyl group-containing monomer.
The performance of the obtained pressure-sensitive adhesive tape was examined by using 1 part by weight of adipic acid dihydrazide as a polyfunctional hydrazide compound as a crosslinking agent in various amounts shown in Table 4. The results are shown in Table 4 below.

[0038]

[Table 4]

[0039]

As described above, according to the present invention, the low-temperature tackiness is 0 or more, the ball tack is 6 or more, the cohesive force is high, there is no adhesive residue, and the creep test holds for 2.5 hours or more. A pressure-sensitive adhesive tape is obtained.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasuo Sudo 3-8-8 Minamihashimoto, Sagamihara City, Kanagawa Sumitomo 3M Co., Ltd. (72) Hirofumi Sonoda 3-8-8 Minamihashimoto, Sagamihara City, Kanagawa Sumitomo 3M Within the corporation

Claims (5)

[Claims] 1. An aqueous emulsion pressure-sensitive adhesive composition obtained by polymerizing a monomer comprising (A) 100 parts by weight of (1) an acrylate monomer and (2) 0.1 to 5 parts by weight of a carbonyl group-containing monomer. A polymer having a glass transition point of −75 ° C. to −45 ° C. and 1 × 10 ⁵
A polymer having a storage modulus of ~ 4 x 10 ⁶ dyn / cm ² .
And (B) a pressure-sensitive adhesive composition comprising the polyfunctional hydrazide compound in an amount of 0.02 to 0.5 mol with respect to 1 mol of the carbonyl group in the carbonyl group-containing monomer of (2). 2. The pressure-sensitive adhesive composition according to claim 1, wherein the alkyl group of the acrylate monomer has 5 to 9 carbon atoms. 3. The water-based emulsion pressure-sensitive adhesive composition according to claim 1, wherein the alkyl group of the acrylate monomer having an alkyl group has 8 or 9 carbon atoms. 4. The polymer (A) further comprises 0.1% sodium p-styrenesulfonate as a monomer component.
1 to 1.5 parts by weight are contained.
The water-based emulsion pressure-sensitive adhesive composition according to any one of 3 above. 5. A pressure-sensitive adhesive tape comprising the substrate and the water-based emulsion pressure-sensitive adhesive composition according to any one of claims 1 to 4 laminated thereon.