JP2003082314A - Aqueous emulsion self-adhesive and self-adhesive sheet obtained by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous emulsion self-adhesive having a low shear viscosity, which enables the manufacture of a self-adhesive sheet having a smooth coated surface without causing cissing and contraction of the aqueous emulsion self-adhesive. SOLUTION: The aqueous emulsion self-adhesive comprises an aqueous dispersion obtained by admixing 0.1-10 pts.wt. of a radical-polymerizable surfactant bearing an unsaturated double bond in the molecule with 100 pts.wt. of a mixture of unsaturated monomers composed of (a), (b) and (c) below, emulsion polymerizing the thus-obtained admixture and further adjusting the pH to 6-10 by incorporating aqueous ammonia, and has a low shear viscosity of at least 50 mPa.s and less than 500 mPa.s: (a) 0.1-5 wt.% of a carboxy group-containing unsaturated monomer, (b) 60-99.9 wt.% of an acrylate ester bearing a 4-12C alkyl group, and (c) 0-40 wt.% of other unsaturated monomers.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to the production of a pressure-sensitive adhesive sheet obtained by applying a water-based emulsion-type pressure-sensitive adhesive to a base material such as a release sheet, which easily causes cissing and blemishes, using a coating device. In addition, the present invention relates to an aqueous emulsion pressure-sensitive adhesive having a low low shear viscosity that does not cause cissing or blemishes of the aqueous emulsion pressure-sensitive adhesive, and a pressure-sensitive adhesive sheet using the same.

[0002]

2. Description of the Related Art Conventionally, adhesive sheets have been processed into labels, stickers, stickers, patches, overlaminate films, protective sheets, etc. for the purpose of marking identification, decoration, masking masking, sealing stickers, information transmission, disaster prevention safety, etc. Widely used for commercial, industrial, office, household and so on. The pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer formed between a surface base material and a release sheet. Usually, paper, film, metal foil, etc. are used for the surface substrate, and glassine paper, clay-coated paper, poly-laminate base paper,
A polyester film, a polyethylene film, or the like coated with a release agent such as a silicon compound is used. As the adhesive, there are solvent type, aqueous emulsion type, hot melt type, etc., and acrylic type, rubber type,
Resin-based materials such as urethane-based and silicon-based are used. Since the application and properties of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet are largely different, the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer is an important factor for characterizing the pressure-sensitive adhesive sheet.

Considering the global environment, the working environment, etc., the water-based emulsion type pressure-sensitive adhesive has been widely used because it is inexpensive and contains almost no organic solvent. On the other hand, in order to improve productivity from the economical viewpoint, there is a demand for increasing the coating speed of the pressure-sensitive adhesive and a demand for reducing the coating amount of the pressure-sensitive adhesive in the production of the pressure-sensitive adhesive sheet. However, in the conventional method for producing a pressure-sensitive adhesive sheet, when an aqueous emulsion-type pressure-sensitive adhesive having a low low-shear viscosity is applied to a release-treated substrate, cissing and blemishes occur, so that an aqueous emulsion having a low low-shear viscosity is obtained. Mold adhesive is used. Therefore, when the coating speed of the aqueous emulsion type adhesive is increased, a rib pattern, cissing, scraping, etc. occur on the coated surface of the aqueous emulsion type adhesive, or defects of fine bubbles due to air entrainment occur, Variations in the coating amount may occur. In particular,
If the variation in the coating amount increases, it becomes difficult to reduce the coating amount of the aqueous emulsion type pressure-sensitive adhesive.

Attempts to increase the coating speed of the water-based emulsion type pressure-sensitive adhesive have been attempted both in terms of improving the coating apparatus and improving the water-based emulsion type pressure-sensitive adhesive. For example, in terms of coating equipment, from conventional revers roll coaters, air knife coaters, knife coaters, comma coaters, etc., such as slot die coaters, lip coaters, and curtain die coaters that press and press the adhesive to apply it to the substrate. Fountain coater has been developed as a coating device suitable for high-speed coating. With the development of the Fountain coater, it has become possible to increase the coating speed to 100 m / min or more. However, the conventional water-based emulsion type pressure-sensitive adhesive has too low a low shear viscosity, so that
In reality, it is not suitable for high-speed coating of 0 m / min or more.

From the viewpoint of an aqueous emulsion type pressure-sensitive adhesive, a method of lowering the low shear viscosity is indispensable in order to improve suitability for high-speed coating. However, when the low shear viscosity is lowered, the cissing when applied to a release sheet is low. This causes problems such as blemishes and streaks, dripping, and excessive spreading of the pressure-sensitive adhesive layer. Therefore, as proposed in Japanese Patent No. 3003317, the low shear viscosity of an aqueous emulsion type adhesive (measured with a B type viscometer at No. 4 rotor / 60 rpm) is 500 mPa · s or more. It needs to be up to. Further, in JP-A-8-218047, an adhesive suitable for high-speed coating is proposed, but as shown in Example 1, it has a low shear viscosity (using a B-type viscometer, No. 4). Rotor / 12 rpm measurement) 8000 m
It says that it should be as high as Pa · s. However, under these conditions, when the coating speed of the water-based emulsion type adhesive is increased, the low shear viscosity (using a B type viscometer, N
o. 4 rotor / 60 rpm) is too high,
At present, it is insufficient for producing an adhesive sheet having a smooth coated surface of the adhesive. In particular, when an aqueous emulsion type adhesive is applied at a speed of 100 m / min or more to produce an adhesive sheet, or when applied at a speed of 100 m / min or more, an adhesive sheet requiring transparency such as an overlaminate film In the case of manufacturing, the finished surface of the pressure-sensitive adhesive coated surface suffers scoring and becomes worse.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and is an adhesive sheet capable of obtaining a smooth coated surface of an adhesive which is free from cissing and blemishes of an aqueous emulsion type adhesive. The present invention aims to provide an aqueous emulsion type pressure-sensitive adhesive having a low shear viscosity and capable of being produced.

[0007]

The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, the following (a):
Unsaturated monomer mixture 100 consisting of (b) and (c)
0.1 to 10 parts by weight of a radically polymerizable surfactant having an unsaturated double bond in the molecule is added to the parts by weight to perform emulsion polymerization, and ammonia water is further added to adjust the pH to 6 to 10. A pressure-sensitive adhesive sheet coated with an aqueous emulsion-type pressure-sensitive adhesive characterized by having a low shear viscosity of 50 mPa · s or more and less than 500 mPa · s, which is composed of the aqueous dispersion obtained by The present invention has been completed and the present invention has been completed. (A) Carboxyl group-containing unsaturated monomer: 0.1 to 5% by weight (b) Acrylic ester having 4 to 12 carbon atoms in the alkyl group: 60 to 99.9% by weight (c) Other unsaturated monomer Weight: 0-40% by weight

[0008]

The present invention will be described in more detail below. The (a) carboxyl group-containing monomer that constitutes the unsaturated monomer mixture is an aqueous dispersion that is indispensable at the time of coating the pressure-sensitive adhesive by adjusting the pH to 6 to 10 with ammonia water after emulsion polymerization. It is used as an essential component for the purpose of imparting mechanical stability to the liquid and improving the film-forming property of the dry film.
Examples of the carboxyl group-containing unsaturated monomer include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, β-carboxylethyl acrylate, and monoesters of 2-hydroxyethyl acrylate and a dicarboxylic acid derivative. It can be used in combination.
Among them, acrylic acid, β-carboxyl ethyl acrylate, and monoester of 2-hydroxyethyl acrylate and a dicarboxylic acid derivative are preferable. The usage is (a),
It is 0.1 to 5% by weight, preferably 1 to 3% by weight, based on the total of components (b) and (c). If the amount used is less than 0.1% by weight, the mechanical stability of the aqueous dispersion decreases, and the emulsion aggregates during coating, causing cissing. Further, the film forming property is deteriorated, and the smoothness of the dry film is deteriorated. On the other hand, if it is more than 5% by weight, the water retention of the film becomes too high and the drying property is lowered. On the other hand, if the pH is less than 6, the mechanical stability of the aqueous dispersion will be reduced, and the emulsion will be aggregated during coating to cause cissing. Further, the film forming property is deteriorated, and the smoothness of the dry film is deteriorated. When neutralized with an alkali neutralizing agent having a high boiling point and having a low volatility other than aqueous ammonia, the neutralizing agent is less likely to volatilize during drying and the drying property is deteriorated. When the pH exceeds 10, the odor is strong and the working environment is burdened, which is not preferable.

The (b) acrylic acid ester having 4 to 12 carbon atoms in the alkyl group constituting the unsaturated monomer mixture is butyl acrylate, 2-ethylhexyl acrylate,
Examples thereof include n-octyl acrylate, isooctyl acrylate, n-nonyl acrylate, isononyl acrylate, and lauryl acrylate, which can be used alone or in combination. Butyl acrylate,
2-ethylhexyl acrylate is preferred. The amount used is 60 to 9 based on the total amount of the components (a), (b) and (c).
It is 9.9% by weight, preferably 70 to 95% by weight.
When the amount used is less than 60% by weight, the tackiness decreases and the tack required as a pressure sensitive adhesive is eliminated.

The (c) other unsaturated monomer may be an unsaturated monomer which constitutes a copolymer of a usual emulsion type pressure-sensitive adhesive, and examples thereof include methyl (meth) acrylate and ethyl (meth). Unsaturated monomers such as acrylate, n-butyl methacrylate, cyclohexyl (meth) acrylate, styrene, α-methylstyrene, acrylonitrile and vinyl acetate can be used according to the purpose. In addition, epoxy group-containing unsaturated monomers such as glycidyl (meth) acrylate and methylglycidyl (meth) acrylate, carbonyl group-containing monomers such as (meth) acrolein and diacetone acrylamide, N-methylol (meth) acrylic amide Etc., a methylol group-containing monomer, an unsaturated monomer having two or more unsaturated double bonds such as divinylbenzene, sodium vinyl sulfonate, sodium styrene sulfonate, 2-acrylamido-2-
Sulfonic acid group-containing monomer such as sodium methylpropanesulfonate, vinylmethoxysilane, vinylethoxysilane, vinyltris (β-methoxyethoxy) silane,
γ-methacryloxypropyltrimethoxysilane, γ-
Use alkoxysilane group-containing monomers such as methacryloxypropyldimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyldimethoxysilane and other unsaturated monomers having functional groups according to the purpose. You can The usage is (a), (b)
It is preferably 0 to 40% by weight based on the total amount of the component (c).

If desired, a chain transfer agent can be used to impart the necessary tackiness as a pressure sensitive adhesive. Specific examples thereof include alcohols such as methanol, ethanol and isoprovir alcohol, and mercaptans such as dodecyl mercaptan and 2-ethylhexyl thioglycolate, which can be used alone or in combination.

Examples of the radical polymerizable surfactant having an unsaturated double bond in the molecule used in the present invention include surfactants represented by the formulas (1) to (11).

[0013]

[Chemical 1]

[0014]

[Chemical 2]

[0015]

[Chemical 3]

Here, R ¹ , R ³ , R ⁴ and R ⁵ are hydrogen or an alkyl group, R ² is an alkyl group or an alkylphenyl group, M is an ammonium salt or potassium,
A metal salt such as sodium, AO is an alkylene oxide including ethylene oxide (EO) and propylene oxide (PO), n is an integer of 0 to 20, and m is 0.
Indicates an integer of -20. Among these, radical polymerizable surfactants having an unsaturated double bond and an ammonium salt of polyoxyalkylene ether sulfuric acid ester in the structure are preferable. Among them, the reactive surfactant, which is a compound represented by the formula (5), the formula (6) or the formula (7), has a high surfactant activity and stabilizes the aqueous dispersion with a smaller amount of the surfactant. Desirable because it can. Examples of the compound represented by the formula (5) include Aqualon KH-10 (Daiichi Kogyo Seiyaku Co., Ltd.).
Manufactured by Asahi Denka Kogyo Co., Ltd. and the like, and the compound represented by the formula (6) includes Adecaria soap SE-10N (manufactured by Asahi Denka Kogyo Co., Ltd.). HS-10 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and the like.

Examples of the compound represented by the formula (10) include Adecaria Soap NE-30 (manufactured by Asahi Denka Kogyo Co., Ltd.), and the compound represented by the formula (11) is Aqualon RN-20. (Manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and the like. The amount of the surfactants represented by the formulas (1) to (11) used is 0.1% with respect to 100 parts by weight of the unsaturated monomer mixture.
1 to 10 parts by weight is used, and preferably 0.2 to 5 parts by weight.

It is possible to use an ionic surfactant or a nonionic surfactant having no unsaturated double bond in the molecule within the range where repelling and tingling do not occur, but it is preferable not to use as much as possible.

In the present invention, as the thickener for adjusting the low shear viscosity, generally used thickeners such as alkali thickeners, associative ones and aqueous polymer thickeners can be used. .

In the present invention, the low shear viscosity is JIS K.
It is a viscosity measured according to the method specified in 6828 (Test method for synthetic resin emulsion), and it must be in the range of 50 mPa · s or more and less than 500 mPa · s. 5
If it is less than 0 mPa · s, cissing and streaks will occur during coating of the pressure-sensitive adhesive, and if it exceeds 500 mPa · s, scoring will occur during coating of the pressure-sensitive adhesive. Particularly, the low shear viscosity is preferably 100 to 490 mPa · s, more preferably 200.
˜460 mPa · s.

The emulsion polymerization can be carried out by using an ordinary initiator, and within a range that does not affect various performances such as occurrence of cissing, fleshing and scoring, depending on the purpose.
Various additives such as antiseptics, defoaming agents, thickeners, cross-linking agents, tackifiers, etc. can be used during or during the emulsion polymerization.

By applying the water-based emulsion-type pressure-sensitive adhesive of the present invention to various known substrates depending on the application, a pressure-sensitive adhesive sheet having a smooth coated surface of the pressure-sensitive adhesive without cissing or blemishes can be provided. it can.

[0023]

EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples. In addition, "part" in an example means a weight part. (Example 1) 14 parts of ion-exchanged water was charged into a container having a stirrer, a thermometer, a reflux condenser, and a dropping funnel at 80 ° C.
The temperature was raised to. On the other hand, 25 parts of ion-exchanged water, 53 parts of butyl acrylate, 1.6 parts of acrylic acid, and Aqualon KH-10 represented by the formula (5) (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
0 part was emulsified with a homomixer to prepare a mixed emulsion (A). 1% of 3% potassium persulfate aqueous solution in the above container
A part was charged and emulsion polymerization was started. Polymerization is 3 with mixed emulsion
% Aqueous potassium persulfate solution (4.3 parts) was added dropwise over 3 hours. During this time, the inside of the container was kept at 80 ° C. After completion of dropping, the mixture was kept at 80 ° C. for 1 hour for aging. After that, cooling is started, and after cooling to 30 ° C., ammonia water is added to
Adjust H to 8 and use ADEKA NOL UH-42 as a thickener.
0 (manufactured by Asahi Denka Kogyo Co., Ltd.) to obtain a low shear viscosity of 4
An aqueous emulsion type pressure-sensitive adhesive A adjusted to 00 mPa · s (measured with a B type viscometer at No. 2 rotor / 60 rpm) was prepared. Using a comma coater (Multi coater manufactured by Hirano Techseed Co., Ltd.), a release sheet (polyamid fine quality paper KP-8 manufactured by Hayashi Kako Co., Ltd.) was coated with the aqueous emulsion type adhesive A at a coating amount of 18 g / m ² ( DRY)
Coating at a coating speed of 10 m / min so that the furnace length is 4
After drying in a drying oven at 100 ° C. for 100 m, fine paper <55> (manufactured by Kishu Paper Co., Ltd.) was pressure bonded to obtain an adhesive sheet. The pressure-sensitive adhesive coated surface of the obtained pressure-sensitive adhesive sheet was free from cissing and scratches, the coated surface was smooth, and the drying property was also good. The results are shown in Table 1.
Shown in.

FIG. 1 is a diagram for explaining the high speed coating machine A used in this embodiment. The high-speed coater A is a device for applying the pressure-sensitive adhesive of the present invention onto a release sheet with a bar coater. Using this high-speed coating machine A, a release sheet (polylaminate high-quality paper KP-8 manufactured by Hayashi Paper Co., Ltd.) was coated with an aqueous emulsion type acrylic emulsion A at a coating amount of 1
The coating was performed so that the amount was 8 g / m ² (DRY), and the presence or absence of cissing and blemishes was observed. As a result, even when the coating speed was 400 m / min, no cissing or scratching was generated on the release sheet, and the coated surface was smooth. The results are shown in Table 1.

Example 2 In Example 1, the formula (1
Example 1 was repeated except that 1 part of Adeka Lithorpe NE-30 (manufactured by Asahi Denka Co., Ltd.) represented by 0) was also used. The results are shown in Table 1.

(Example 3) In Example 1, Aqualon KH-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added to ADEKA RESORP SE-10N (Asahi Denka Kogyo KK) represented by the formula (6).
The same as Example 1 except that the manufacturing method was changed. The results are shown in Table 1.

(Example 4) The same procedure as in Example 1 was repeated except that β-carboxyethyl acrylate was used instead of acrylic acid. The results are shown in Table 1.

(Comparative Example 1) In Example 1, Aqualon KH-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used as Hitenol 08E, an anionic surfactant having no unsaturated double bond in the molecule. The same procedure as in Example 1 was carried out except that (Daiichi Kogyo Seiyaku Co., Ltd.) was used. The results are shown in Table 2.

(Comparative Example 2) In Example 1, AQUALON KH-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), which is a nonionic surfactant having no unsaturated double bond in the molecule, is Emage 931. The same procedure as in Example 1 was performed except that the product was changed to (manufactured by Kao Corporation). The results are shown in Table 2.

(Comparative Example 3) The same procedure as in Example 1 was carried out except that acrylic acid was changed to 0 part in Example 1. The results are shown in Table 2.

(Comparative Example 4) In Example 1, the pH was adjusted to 5
The same procedure as in Example 1 was carried out except that the above adjustment was made. The results are shown in Table 2.

(Comparative Example 5) The same procedure as in Example 1 was carried out except that the aqueous ammonia was changed to sodium hydroxide. The results are shown in Table 2.

Comparative Example 6 The procedure of Example 1 was repeated, except that the low shear viscosity was set to 5000 mPa · s (measurement with B-type viscometer No. 4 rotor / 60 rpm). The results are shown in Table 2.

(Comparative Example 7) In Example 1, a low shear viscosity of 40 mPa · s (B type viscometer No. 1 rotor /
The same procedure as in Example 1 was performed except that the measurement was performed at 60 rpm. The results are shown in Table 2.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

The aqueous emulsion type pressure-sensitive adhesive of the present invention comprises
Although the low shear viscosity is low, it is possible to obtain a smooth pressure-sensitive adhesive coated surface free from cissing and blemishes. In particular,
Even the release paper, which is the base material whose surface is treated for release, is 100m
With a high-speed coating of not less than 1 minute, a smooth pressure-sensitive adhesive coated surface free of cissing and blemishes can be obtained. As a result, the smoothness of the PSA coated surface of the PSA sheet can be significantly improved. Furthermore, since the coating speed of the pressure-sensitive adhesive can be increased to 100 / min or more, the productivity can be remarkably improved.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a high-speed coating machine A used in Examples and Comparative Examples.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tetsuya Onishi             4-6-14 Jomidai, Himeji City, Hyogo Prefecture (72) Inventor Haruki Nishiike             199-85, Nakamura, Tatsuno-cho, Tatsuno-shi, Hyogo F-term (reference) 4J004 AA10 AB01 CA00 DB02                 4J011 KA06 KA14 KB14 KB29                 4J040 DF041 GA07 GA11 GA21                       GA22 GA25 GA29 JA03 JB09                       KA38 LA01                 4J100 AB02Q AJ02Q AJ08Q AJ09Q                       AL03P AL03R AL04P AL05P                       AM02R CA04 CA05 FA20                       JA03

Claims (2)

[Claims] 1. A radical-polymerizable surfactant having an unsaturated double bond in its molecule in an amount of 0.1 parts by weight per 100 parts by weight of an unsaturated monomer mixture consisting of the following (a), (b) and (c).
A low shear viscosity of 50 mPa · s or more, 500, which comprises an aqueous dispersion obtained by mixing 1 to 10 parts by weight and emulsion-polymerizing, and further adding ammonia water to adjust the pH to 6 to 10
An aqueous emulsion type pressure-sensitive adhesive characterized by having a viscosity of less than mPa · s. (A) Carboxyl group-containing unsaturated monomer: 0.1 to 5% by weight (b) Acrylic ester having 4 to 12 carbon atoms in the alkyl group: 60 to 99.9% by weight (c) Other unsaturated monomer Weight: 0-40% by weight 2. A pressure-sensitive adhesive sheet obtained by applying the aqueous emulsion-type pressure-sensitive adhesive according to claim 1 on a substrate.