JPS5818959B2 - Pressure sensitive adhesive tape or sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure-sensitive adhesive tape or sheet, and more specifically, to the surface of various articles, especially the surface of textile products such as paper or fabric, for adhesive and peeling purposes. The present invention relates to a pressure-sensitive adhesive tape or sheet whose adhesive strength does not easily decrease even after repeated cycles.

Pressure-sensitive adhesive tapes are useful because they can be easily attached to the surface of any article, and in some cases, they can be reattached once peeled off. In the case of paper, once it is peeled off, fibers will adhere to the adhesive, reducing its adhesive strength and making it difficult to re-stick it.In particular, in the case of paper, if you try to peel it off, it will cause what is called a paper-tearing situation, which can be very serious. The equations that cause paper to break when something is wrong are something we experience every day.

The present invention eliminates the drawbacks of conventional pressure-sensitive adhesive tapes as described above, and provides a tape that can be reliably attached to the surface of textile products and can be repeatedly applied and peeled off. with the purpose of providing
The gist is (a) alkyl group (7) 80 to 98% by weight of one or more types of acrylic acid alkyl ester or methacrylic acid alkyl ester having 4 to 12 carbon atoms;
b) A copolymer solution obtained by polymerizing 2 to 20% by weight of one or more α-monoolefin carboxylic acids (a) and (b) in a solvent is placed in water containing metal ions. The present invention is a pressure-sensitive adhesive tape or sheet in which a large number of adhesive microparticles are attached to the surface of a substrate by applying the resulting suspension onto the surface of the substrate and drying it.

The base material for the pressure-sensitive adhesive tape or sheet of the present invention is not particularly limited (in addition to fibers such as paper, fabric, and nonwoven fabric, it may also include polyethylene, polypropylene, polyester, polyvinyl chloride, cellulose acetate, cellophane, etc.). Examples include smooth films and sheets.

However, as the adhesive microparticles used in the present invention, those with large elastic deformation or plastic deformation generally have thick adhesiveness (
However, such soft adhesive microparticles can be crushed and piled up during the work of adhering them to the surface of the substrate or over time afterwards. It is easily deformed in shape, and furthermore, it tends to completely collapse when it is attached to an adherend or over time in the attached state, resulting in a state close to a continuous flat adhesive surface, which is not suitable for the purpose of the present invention. It is something.

Therefore, the adhesive microparticles used in the present invention need to have adhesive force and internal cohesive force to the extent that the above-mentioned deformation does not occur.

Therefore, in the present invention, in order to provide adhesive strength, one of acrylic acid alkyl ester or methacrylic acid alkyl ester whose alkyl group has 4 to 12 carbon atoms is used.
species or two or more species... (a) using a monomer,
In addition, in order to provide an internal cohesive force to the extent that the deformation does not occur, one or two α-monoolefin carboxylic acids are used.
More than one species...(b) Monomers are used,
The internal cohesive force of the copolymer of these vehicle bodies is still insufficient, and furthermore, the carboxyl group introduced into the copolymer by using the above-mentioned rb) monomer is It must be crosslinked by ions, thereby improving its internal cohesive force.

As the monomer (a), any monomer can be used as long as the number of carbon atoms in the alkyl group is within the range of 4 to 12, but butyl acrylate, 2 Examples include ethylhexyl acrylate and lauryl acrylate.

Examples of the (b) monomer, ie, α-monoolefin carboxylic acid, include acrylic acid, methacrylic acid, itaconic acid, maleic acid, and crotonic acid.

Therefore, in this case, it is necessary that the monomer (b) be contained within the range of 2 to 20% by weight of the total amount, and if it is less than 2% by weight of the total amount, sufficient internal cohesive force is required. If the amount exceeds 20% by weight, sufficient adhesive strength cannot be obtained.

In addition, as a monomer for obtaining the copolymer, the above fa)
, rb) In addition to both polymers, in order to adjust adhesive force and cohesive force, acrylic acid alkyl esters or methacrylic acid alkyl esters having an alkyl group having 1 to 3 carbon atoms, vinyl acetate, vinyl propionate, styrene, acrylonitrile,
It is also effective to use a small amount of one or more of acrylamide, 2-hydroxyethyl acrylate, and 2-hydroxyethyl methacrylate.

In addition, in order to crosslink the copolymer used in the present invention with metal ions, metal ions must be included in water in advance (possibly It will be done.

In the pressure-sensitive adhesive tape or sheet of the present invention, adhesive microparticles made of the above-mentioned copolymer are applied directly to the substrate or via an undercoat made of acrylic resin, saturated polyester resin, polybutyral resin, epoxy resin, etc. The diameter of the adhesive microparticles is preferably within the range of 50 to 100μ, and the amount of the adhesive particles is as follows:
The appropriate dry amount is 5 to 10 grams per square meter.

When using an undercoat, the preferred ratio of the adhesive microparticles to the undercoat in terms of weight ratio (dry amount) is 10 for the former to 2 for the latter when the base material is smooth and non-impregnable. ~5
When the base material is impregnable such as paper or cloth, the former is 10 and the latter is 10 to 25. In such a case, the base material is sufficiently impregnated with a primer solution in advance and dried to reduce its impregnability. Adhesion of adhesive microparticles can be made easier by making it similar to a smooth film, and when the adhesive microparticles are adhered to the undercoat layer, the lower part of the undercoat layer is soft. immersed in the undercoat layer, and when the undercoat layer is hard, the bottom becomes flat and has a slightly crushed shape.

Therefore, when a tape or sheet to which a large number of such adhesive microparticles are attached is attached to the surface of paper and then peeled off, the paper can be peeled off without causing tearing (peeling is done, and reattachment is also possible). The reason is that because adhesive microparticles with a diameter of 50 to 100 μm are attached to the surface of the base material, the fiber It is easier to adhere to the surface of paper with an intertwined structure, and it adheres more reliably.
In addition, since point adhesion is used, the range in which the fibers are pulled during peeling is limited to a narrow range, making it difficult for the paper tearing phenomenon to occur.

Next, a method for obtaining the above-mentioned suspension of sticky microparticles will be explained.

First, monomers (a) and (b) are polymerized in a solvent such as an organic solvent such as ethyl acetate to obtain a copolymer solution.

This solid content concentration is 40-50%, and the viscosity is 3000-10
It is preferably within the range of 0,000 centivoices, and if necessary, it may be prepared by further diluting the polymerization product with an organic solvent such as toluene.

Next, the solution of the copolymer thus obtained is poured into water in order to obtain sticky microparticles of the copolymer.

The weight ratio at this time is 25 parts copolymer solution to 100 parts water.
~100 is appropriate.

The copolymer solution is then made into a dispersed suspension by mechanical methods such as stirring, but in order to facilitate the dispersion and stabilize the suspension, a long-chain alkyl alcohol sulfate ester soda or the like is added to the water in advance. Add anionic surfactant to 1 part water.
00 to 0.00, or an oil-soluble nonionic surfactant such as polyethylene glycol alkyl ether or polyethylene glycol alkyl allyl ether to 100 parts of the copolymer solution.
It is preferable to dissolve it in a weight ratio of about 0.2 parts to 1 part.

Therefore, in order to crosslink the copolymer with metal ions, Mg 2 +, ca 2+,
sn2+, Sn", Fea+, co2+, Ni", zn
A metal salt or hydroxide capable of providing divalent or higher valence metal ions such as 2+, A13+, etc., which is soluble in water and does not leave a nonvolatile residue, is dissolved.

Specific examples include formates and acetates of Mg1Ca and Zn, and calcium hydroxide.

Calcium hydroxide has a high solubility in water (although it does not have a high solubility in water), as the initially dissolved substance reacts sequentially with the carboxyl groups in the copolymer, dissolution progresses and eventually all of the copolymer reacts.

Monovalent metal ions, such as Na10 and K10, are not preferred because they do not provide the same crosslinking effect as divalent or higher valent ions and also have the function of reducing the adhesive strength of the copolymer.

The amount of metal ions added to water varies depending on the content of carboxyl groups in the copolymer added to the water, and an amount that neutralizes 5 to 60% of the carboxyl groups is appropriate.

When the carboxyl group content of the copolymer is low, the neutralization rate with metal ions may be increased, and in the opposite case, it may be decreased.

In addition, when polymerizing both polymers (a) and rb) using a solution polymerization solution, it is possible to include metal ions in the solvent and cause ionic crosslinking at the same time during the polymerization process. If the crosslinking is carried out before the formation of fine particles, the resulting fine particles will not have excellent internal cohesive force, especially near the outer surface, which is not preferable.

Next, in order to obtain a suspension of the copolymer solution in water, it is preferable to gradually add water containing metal ions into the copolymer solution while stirring the copolymer solution in a container.

In addition, by heating and boiling while stirring to remove part or all of the solvent, the shape and diameter of the sticky microparticles obtained become more uniform, and the stability of the suspension is also improved.

If the suspension thus obtained is applied directly to the surface of the base material or on the surface of the base coat layer of a base coated with a base coat in advance and dried, the suspension will be suspended on the surface of the base material or the base coat layer. A pressure-sensitive adhesive tape or sheet of the present invention having a structure in which adhesive microparticles in liquid form are adhered in a discontinuous dot pattern in substantially the same shape as before is obtained.

In addition, if the coating thickness on the substrate surface is thick, the adhesive microparticles will be formed in multiple layers, but if possible, it is preferable to reduce the coating thickness and form a single layer.

The surface of the substrate to which the adhesive microparticles are attached may be only one side or both sides of the substrate, and the adhesive microparticle surface is protected by a suitable release paper.

The pressure-sensitive adhesive tape or sheet of the present invention has an adhesive surface formed of a large number of adhesive microparticles, and the microparticles are made of a copolymer having both appropriate adhesive strength and internal cohesive force. Even if the adherend is a textile product such as paper or fabric, the fibers will not be removed from the adhesive surface when it is peeled off after pasting, and the cycle of pasting and peeling can be repeated, making it easy to remove paper. It does not damage the adherend, and the adhesive force and internal cohesive force are balanced, so that the adhesive microparticles are not crushed when applied to the base material or due to aging in the adhered state. It is easy to manufacture and has excellent quality stability.

In addition, the pressure-sensitive adhesive tape or sheet of the present invention can be produced by dispersing a solution of a copolymer into which carboxyl groups have been introduced in the copolymer forming the adhesive microparticles in water containing metal ions to form ionic cross-links between molecules. This method is technically easier than other methods of obtaining internal cohesive force.

This will be explained below with reference to examples.

It should be noted that all references to "Example Middle" refer to parts by weight.

Example 1 100 parts of ethyl acetate was placed in a reactor, heated to boiling point while stirring, and 40 parts of di-tylhexyl acrylate, 52.5 parts of butyl acrylate, and acrylic acid were added to the reactor while stirring. First, 1/4 of a mixture of 2.5 parts of ethyl acrylate, 5 parts of benzoyl peroxide, and 0.12 parts of benzoyl peroxide was added at once, and the same amount was added every hour thereafter while heating, refluxing and stirring continued. and allow polymerization to proceed.

At this time, the temperature of the liquid in the reactor required to continue refluxing increases gradually and reaches 95° C. after the final addition.

After the last addition is completed, the reaction is continued in the same manner for another 3 hours, and after the polymerization is completed, the mixture is cooled to room temperature.

The copolymer thus obtained had a concentration of 49.1% and a viscosity of 20,000 centivoices, and was further diluted with toluene to a concentration of 35%.

Next, in order to form the copolymer solution into sticky fine particles, it is placed in a container and while stirring, a solution prepared by dissolving 0.8 parts of lauryl alcohol sulfate ester soda in 150 parts of water is gradually added.

After the viscosity of the liquid in the container rose once and then decreased until it became close to the viscosity of water itself, 0.23 parts of calcium hydroxide was added little by little into the container and continued to stir rapidly for another hour. A dispersed suspension of a copolymer partially crosslinked with calcium ions was obtained.

At this time, about 50% of the carboxyl groups in the copolymer were ionically bonded.

Meanwhile, 20% of linear saturated polyester resin as a primer
A toluene solution was prepared.

Next, the above primer was applied to the surface of a 38μ thick polyester film at an amount of about 151 grams per square meter and allowed to dry, and on top of this primer layer, the suspension was coated at an amount of 56 grams per square meter and dried. It was made into a pressure-sensitive adhesive sheet.

(The dry coating amount of the base coat of the pressure-sensitive adhesive sheet and the adhesive microparticles obtained by
? The diameter of the adhesive microparticles is mostly 50 to 150
It was within the range of μ.

Comparative Example 1 A pressure-sensitive adhesive sheet with adhesive microparticles having a diameter of 50 to 100 μm was obtained in the same manner as in Example 1, except that calcium hydroxide was not added in the process of producing an aqueous suspension.

Example 2 (a) and rb) The mixture of monomers and polymerization initiator was 50 parts of 2-functional tylhexyl acrylate, 47 parts of butyl acrylate, 3 parts of methacrylic acid, and 0.12 parts of benzoyl peroxide. Polymerization was carried out in the same manner as in the example, and the concentration was 48.
．． A copolymer solution with a viscosity of 0% and a viscosity of 16,000 centivoice was obtained.

This was further diluted with toluene to give a concentration of 35%.

Next, the above copolymer solution was placed in a container, and while stirring, 0.2 part of polyethylene glycol nonylphenyl ether, which is a nonionic surfactant, was added, and further 0.6 part of lauryl alcohol sulfate ester soda was added to 150 parts of water. A solution containing 0.67 parts of zinc acetate trihydrate and 0.67 parts of zinc acetate trihydrate was gradually added, and stirring was continued rapidly for an additional hour to form a dispersed suspension of the copolymer partially crosslinked by zinc ions. Obtained.

At this time, about 50% of the carboxyl groups in the copolymer were ionically bonded.

On the other hand, as a primer, the average degree of polymerization is 1500, and the degree of saponification is 35%.
A 10% aqueous solution of polyvinyl alcohol was prepared and used as a primer.

Next, apply the above primer to the surface of 300μ thick kraft paper at a rate of 50' per square meter. After coating and drying, the suspension was applied on top of this primer layer at a rate of 63°C per square meter. A pressure-sensitive adhesive sheet was obtained by coating and drying.

The dry coating amount of the base coat of the pressure-sensitive adhesive sheet and the adhesive microparticles thus obtained was approximately 5.91 per square meter, respectively.
The diameter of the adhesive microparticles is mostly 50 to 150μ.
was within the range.

Comparative Example 2 A pressure-sensitive adhesive sheet with adhesive microparticles having a diameter of 50 to 100 μm was obtained in the same manner as in Example 2, except that zinc acetate trihydrate was not added in the process of producing an aqueous suspension.

The performance of the pressure-sensitive adhesive sheets obtained in each of the above Examples and Comparative Examples is shown in the following table.

All measurements in the following table were conducted in a measurement room under constant temperature conditions of 20°C.

Claims (1)

[Claims] 1(a) 1 of acrylic acid alkyl ester or methacrylic acid alkyl ester having an alkyl group having 4 to 12 carbon atoms
species or two or more species 80 to 98% by weight, rb) one or two or more α-monoolefin carboxylic acids 2 to 20%
A copolymer solution obtained by polymerizing both polymers (a) and (b) in a solvent with a weight percent or more is dispersed in water containing metal ions, and the suspension obtained is applied to the surface of the base material and dried. A pressure-sensitive adhesive tape or sheet made by attaching a large number of adhesive microparticles to the surface of a base material.