JPS607670B2 - Method of manufacturing pressure sensitive adhesive tape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a pressure sensitive adhesive tape.

A solution-type acrylic adhesive composition in which an acrylic copolymer and a polyfunctional isocyanate are dissolved in an organic solvent is known as a pressure-sensitive adhesive used in a pressure-sensitive adhesive tape.

However, in recent years, due to problems such as air pollution caused by volatilization of organic solvents, there has been a demand for a solvent-free method.

Generally, it is difficult to add a polyfunctional isocyanate to an acrylic copolymer using water as a medium, and even if it were possible to add it, it would react with water before the functional groups of the copolymer and NCO groups react. There is a problem that it cannot be used as an adhesive composition because it is stored away. For this purpose, for example, in the water-dispersed adhesive disclosed in JP-A-51-93936, isocyanate is added to an acrylic polymer using water as a medium, and isocyanate has almost no mutual solubility with water. An adhesive is prepared by mixing a solution in which the NCO group is protected from water using an organic solvent that has mutual solubility with the NCO group.

This invention provides an acrylic water-based adhesive composition without using any or many organic solvents, and after forming this composition on a support, two steps are carried out sequentially under specific heating conditions. The present invention provides a novel manufacturing method for producing pressure-sensitive adhesive tapes.

To explain the details of this invention more specifically, an aqueous dispersion or solution of an acrylic copolymer containing active hydrogen capable of reacting with an NCO group in its side chain or primary mirror is added to An aqueous adhesive composition prepared by adding a regenerated isocyanate obtained by stabilizing a polyfunctional isocyanate containing the above with a masking agent containing active hydrogen in the form of an aqueous dispersion is coated on a support and/or co-immersed, 50
The first step is drying for 0.5 to 10 minutes under heating conditions of ~10 qo, and drying for 0.5 to 10 minutes under heating conditions of 140 qo or more.
and a second step of partially crosslinking the composition by drying the composition for a few minutes.

Therefore, when a pressure-sensitive adhesive tape is manufactured using a known moisture-based adhesive composition, it is very difficult to balance the adhesive strength, adhesive strength, and cohesive strength of the pressure-sensitive adhesive. In contrast, the pressure-sensitive adhesive tape obtained by the method of the present invention has a feature that it can have these properties in a well-balanced manner.

The aqueous dispersion or solution of an acrylic copolymer containing active hydrogen capable of reacting with an NCO group in the side chain or main chain of the molecule used in this invention serves as a base for a pressure-sensitive adhesive and is produced according to a conventional method. Ru.

That is, one or more monomers having a polymerizable ethylenically unsaturated bond having at least one functional group capable of reacting with an NCO group such as a carboxyl group, a hydroxyl group, an amino group, or an amide group, and an alkyl For a monomer consisting of an acrylic acid alkyl ester whose group has less than 1 carbon number, an emulsifier such as an anionic type, a mixture of a nonionic type and an anionic type, and water are added to a monomer with a solid content of 20
It can be obtained by adding a water-soluble catalyst to the mixture to a concentration of ~35% by weight, and heating and reacting the mixture. In the method for producing the aqueous acrylic copolymer dispersion or solution, it goes without saying that, for example, the monomers used may be charged in portions, or the water-soluble catalyst may be charged in portions and reacted. As the above-mentioned ethylenic monomer, for example, the following can be used.

(1) Ethylenically polymerizable monomer having a carboxyl group,
Examples include acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, m) ethylenically polymerizable monomers with hydroxyl groups, examples include acrylic acid-2-hydroxyethyl ester, acrylic acid-2-hydroxy Propylester, methacrylic acid-2-hydroxyethyl ester, methacrylic acid-2-hydroxyph.

Lopyle ester, (m) Ethylenically polymerizable monomer having an amino group, such as N・N-dimethylaminoethyl acrylate, N-tert-butylaminoethyl acrylate, aminoethyl vinyl ether, (N) having an amide group Ethylenically polymerizable monomers, such as acrylamide and methacrylamide, and acrylic acid alkyl esters, such as ethyl acrylate, methyl acrylate, butyl acrylate, isooctyl acrylate, and 2-ethylhexyl acrylate, have a carbon alkyl group. It is preferable to use a lower acrylic acid alkyl ester having a number of 12 or less from the viewpoint of adhesiveness, but in some cases, a methacrylic acid alkyl ester or styrene that can be copolymerized with a monomer having an ethylenically unsaturated bond is used. Appropriate amounts of monomers such as , styrene, and vinyl acetate may also be added.

As an emulsifier, a nonionic surfactant such as polyoxyethylene alkyl ether or alkylphenol ether may be used alone, or the nonionic surfactant and higher alcohol sulfate ester salt, polyethylene glycol ether sulfate ester salt, etc. Mixtures with anionic surfactants such as sulfates such as sulfates and alkylaryl sulfonates are preferably used.

As the water-soluble catalyst, ammonium persulfate, potassium persulfate, hydroperoxide, etc. are preferably used.

The regenerated isocyanate used in this invention is obtained by stabilizing a polyfunctional isocyanate containing two or more NCO groups in the molecule with a masking agent containing active hydrogen. This is what I did.

Such a regenerated product can be obtained by reacting a polyfunctional isocyanate with a masking agent, usually using about 1.05 to 1.15 moles of the masking agent per NCO group in the polyfunctional isocyanate. That is, a polyfunctional isocyanate and a desired amount of a masking agent are further mixed in the presence or absence of an inert solvent such as an ester such as ethyl acetate or butyl acetate, or a ketone such as methyl ethyl ketone or methyl isobutyl ketone. If so, they are generally prepared by reaction in the presence of a catalyst such as a tertiary amine at about 50 to 170 qO. Specific examples of the diisocyanate used in the production of the regenerated isocyanate used in the method of the present invention are as follows. (1) Aliphatic diisocyanates, such as hexamethylene diisocyanate, ethylene diisocyanate, 1,4-butane diisocyanate, 1,6-hexane diisocyanate, and modified products thereof; (0) Alicyclic diisocyanates, such as dicyclohexylmethane Diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate and modified products thereof (m) Aromatic diisocyanates, such as 2,4 and 2,6-tolylene diisocyanate, 4,4'-diphenyl ether diisocyanate , 4,4'-difhenylmethane diisocyanate, m-xylylene diisocyanate and modified products thereof, and these isocyanates may be used alone or as a mixture of two or more.

Masking agents used to produce the regenerated isocyanate used in the method of this invention include masking agents used to stabilize isocyanates, such as phenol-based, alcohol-based, amide-based, acin-based, and lactam-based masking agents. , mercaptan-based, active methylene-based, and sulfite-based masking agents can be used, but in particular, phenol-based, lactam-based, and active methylene-based masking agents are preferably used, and the release temperature of the NCO group is 100° C. or higher.

The following are used as specific examples of masking agents. (1
) Phenol-based masking agents, such as phenol, cresol (0) Lactam-based masking agents, such as cabrotactam blood) Active methylene-based masking agents, such as gestal malonate, ethyl acetoacetate These isocyanate regenerants have 0 particle sites. .001 french to 10 m preferably 0.0
01 to 1, and mixed with water in an amount of about 0.1 to 10% by weight based on the total weight in the presence or absence of an emulsifier to prepare an aqueous dispersion.

The acrylic copolymer aqueous dispersion or aqueous solution and the isocyanate regenerant aqueous dispersion prepared in this way have a solid content of 10 parts by weight for the former and -0.05 parts for the latter.
-2 parts by weight, preferably 0.1-1 parts by weight, to prepare an aqueous adhesive composition.

If the latter is less than 0.05 parts by weight, the crosslinking effect of the pressure-sensitive adhesive obtained by crosslinking with heat will be insufficient, the cohesiveness will be poor, and the heat resistance and solvent resistance will be poor, so it is not preferable. Above this amount, the crosslinking becomes excessive and the adhesiveness becomes weak, making it unsuitable as a pressure-sensitive adhesive. The aqueous adhesive composition includes:
As a reaction accelerator for NCO groups, organic acids such as adipic acid, acetic acid, and oleisic acid, or dibutyltin, dilaurate, dibutyltin di(2-ethylhexoate), stannous 2-ethylcabutanoate, and stannic chloride are used. Appropriate amounts of organometallic compounds can be added.

The composition may also contain fillers for special effects.
Coloring agents and the like can be added.

The support to which the aqueous adhesive composition is applied and/or impregnated includes plastic, paper, cloth (non-woven fabric, woven fabric,
(including knitted fabrics), metal sheets, resin-treated paper with low adhesion properties, thin materials made of inorganic materials, etc., and laminated films and sheets of these materials can also be used. The aqueous adhesive composition is formed on the support using commonly known coating and/or impregnating equipment.

In order to convert the coated and/or impregnated water-based low viscosity composition into a highly viscous cohesive adhesive layer with good heat and solvent resistance, the coating and/or impregnating composition is coated on the support. The composition formed in
under the first heating condition for 0.5 to 10 minutes, preferably 75
It is heated for 3 to 5 minutes at ~95 qo.

Immediately after passing through the above heating conditions, a second heating condition of at least 140 o'clock, preferably at least 160 o'clock is applied.
．． Allow to heat for 5 to 10 minutes, preferably 3 to 8 minutes. In the first heating step, substantially all of the water in the aqueous adhesive composition formed on the support is removed from the NC of the isocyanate regenerated product.
It disperses the O group without liberating it,
The second heating step releases the NCO groups of the regenerated isocyanate from the masking agent, partially crosslinks the NCO groups and the functional groups of the acrylic copolymer, and increases the anchoring force between the pressure sensitive adhesive and the support. The present invention provides a pressure sensitive adhesive tape having a pressure sensitive adhesive with enhanced adhesion, tack and cohesive strength.

Examples of this invention will be shown below.

This invention is not limited to the following examples. Example 1 50% of 2-ethylhexyl acrylate and 2% of acrylic acid.
At 5pm, a thermometer, a Nadayo machine, a N2 introduction pipe and a cooler were installed.
Stir thoroughly in a 00cc flask, add 1.5 # of polyoxyethylene alkyl phenol ether salt (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name Noigen EA-1900), stir thoroughly, and then add 200cc of water. Then, in a N2 stream, 105 parts of ammonium persulfate (a water-soluble catalyst) was added, and while the flask was cooled from the outside, the flask was polymerized at 7 degrees for 6 hours to form an acrylic copolymer with a solid content of about 30% by weight. An aqueous dispersion (average molecular weight of about 100) is obtained.

To 100 parts by weight of the solid content of the aqueous dispersion, 2 parts of regenerated hexamethylene diisocyanate whose NCO groups were stabilized using m-cresol as a masking agent were added to give 30 parts by weight.
C. for 20 minutes to obtain an aqueous adhesive composition.

This composition was applied onto a resin-treated paper with low adhesion to a dry thickness of 50°C, first dried at 80°C for 3 minutes, and then further dried at 150°C for 3 minutes to form a pressure-sensitive adhesive tape. Obtained.

A sample piece was prepared by pasting the pressure-sensitive adhesive film of this adhesive tape on a 12-piece polyester tape and cutting it into two broadsides.The resin-treated paper was peeled off and the adhesive strength and adhesion strength were measured using the following method. The cohesive force was measured.

Adhesion force measurement method and measured values A 2 kg sample piece was placed on a #280 sandgrasted stainless steel plate.
After adhering with a rubber roller of
When a 180°C peel test was conducted at a rate of 0.00 mm/min), it showed an adhesive strength of 980 mm/2 rib widths.

Adhesive force measurement method and measured value Based on the rolling ball method of J.

That is, a sample piece of a certain length is fixed on a slope with an angle of 30 degrees, and a sample piece of 32 mm from 1/32 inch to 1 inch is placed above a certain height.
A steel ball the size of a bell is rolled, and the No. 1 ball with the largest diameter stops on one side. When the adhesive strength was measured, No. It turned out that 27 stopped. Cohesive force measurement method and measured value Place one end of the sample piece (width 2 m) on the edge of the stainless steel plate mentioned above.
When we measured the displacement distance of a sample piece that was pasted on the edge of a pond, a load of 500 kg was applied to the edge of the pond, and the specimen was left at 40°C for 2 hours, it was found to be 0.
It had 5 ribs.

As is clear from Example 1, it is remarkable that the pressure-sensitive adhesive tape obtained by the production of the present invention has a balance in adhesive strength, adhesion strength, and cohesive strength that allows it to be suitably used as an adhesive tape. .

Example 2 50 ml of butyl acrylate and 2.5 ml of 2-hydroxyethyl acrylate were sufficiently mixed in the 500 cc flask, and then polyoxyethylene alkylphenol ether salt (Nygen) was added in the same manner as in Example 1. EA-19
00) 1.59, 200 cc of water, and 105 parts of ammonium persulfate are added to obtain an aqueous acrylic copolymer dispersion (average molecular weight of about 1 million) having a solid content of about 3% by weight.

To 100 parts by weight of the solid content of the aqueous dispersion, 2 parts of the regenerated hexamethylene diisocyanate of Example 1 was added to give 30 parts by weight.
00 for 2 hours to obtain an aqueous adhesive composition.

This composition was applied onto resin-treated paper so that the thickness after drying was 50 mm, and first dried at 90 qo for 2.5 minutes.
It was further dried at 150° C. for 3 minutes to obtain a pressure-sensitive adhesive tape.

A sample piece of the pressure-sensitive adhesive film of this adhesive tape was prepared in the same manner as in Example 1, and its characteristics were measured.

Measurement result

Claims (1)

[Claims] 1 Add active hydrogen to a polyfunctional isocyanate containing two or more NCO groups in the molecule to an aqueous dispersion or solution of an acrylic copolymer containing active hydrogen that can react with NCO groups in the side chain or main chain of the molecule. A support is coated with and/or impregnated with an aqueous adhesive composition prepared by adding a regenerated isocyanate stabilized with a masking agent in the form of an aqueous dispersion, and heated to a temperature of 50 to 100°C. The first step is drying for 5 to 10 minutes, and the heating condition is 0.
．． A second step of partially crosslinking the composition by drying for 5-10 minutes.
A method for producing a pressure-sensitive adhesive tape, comprising the steps of: