JP2516019B2 - Removable adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention comprises an acrylic pressure-sensitive adhesive containing a silicone / acrylic block copolymer, and is excellent in removability and non-staining property to an adherend, and surface protection. The present invention relates to a removable pressure-sensitive adhesive suitable for materials and the like.

Conventional technology and problems Conventionally, a phosphoric acid ester-based or amine-based surfactant has been blended with an acrylic pressure-sensitive adhesive to suppress an increase in the adhesive strength with time on the adherend, and thereby prevent the adhesive from re-adhering on the adherend. It was known that the peeling was easy.

Further, in the method of blending the above-mentioned surfactant in the pressure-sensitive adhesive, the peeling property is likely to vary, so that the surfactant occupies the surface of the pressure-sensitive adhesive layer, so that the surface-active agent on the back surface of the supporting base material It is also known that an agent layer is provided (JP-A-55-38841).

However, any of the above methods has a problem that the surface of the adherend is contaminated with the surfactant.

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to develop a removable pressure-sensitive adhesive that does not easily cause such a pollution problem, and as a result, use a special silicone-acrylic block copolymer. As a result, they have found that the object can be achieved, and have completed the present invention.

That is, the present invention provides a removable pressure-sensitive adhesive characterized in that a block copolymer having a block unit made of polydiorganosiloxane and a block unit made of an acrylic polymer is mixed in the acrylic pressure-sensitive adhesive. It is a thing.

Action The block copolymer described above is difficult to separate from the acrylic pressure-sensitive adhesive and has an excellent effect of suppressing the increase in adhesive strength over time. This is excellent in compatibility or bonding force with the acrylic pressure-sensitive adhesive based on the block portion made of acrylic polymer, on the other hand, the block portion made of polydiorganosiloxane is more likely to be alienated than the acrylic pressure-sensitive adhesive,
It is considered that this is because the polydiorganosiloxane component in the copolymer on the surface of the pressure-sensitive adhesive layer is easily located on the surface of the pressure-sensitive adhesive layer.

Examples of Components of the Invention The block copolymer used in the present invention has a block unit composed of a polydiorganosiloxane and a block unit composed of an acrylic polymer.

The polydiorganosiloxane, which is one of the block units, is composed of an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group, an aryl group, an organic group such as an aralkyl group, which is bonded to a silicon atom. Molecular weight 1,
Those of 000 to 50,000 are suitable. Its number average molecular weight is
If it is less than 1,000, the effect of imparting removability is poor, and if it exceeds 50,000, it is easy to separate from the adhesive, which is not preferable.

The other block unit, an acrylic polymer, is composed of a polymer or copolymer containing an alkyl ester of acrylic acid or methacrylic acid as a component. The preferred block unit has a composition in which an acrylic acid ester component having an alkyl group having 1 to 12 carbon atoms accounts for 60% by weight or more. Monomer components other than acrylic acid ester components
A composition that accounts for 40% by weight or more is not preferable because it easily separates from the acrylic pressure-sensitive adhesive. The number average molecular weight of the acrylic polymer that constitutes the block unit is 1,000 to 1.
About 00,000 is suitable, but not limited to this.

Specific examples of the acrylic acid-based alkyl ester that is commonly used as a component that constitutes the acrylic-based polymer include:
Examples thereof include acrylic acid and methacrylic acid esters having a methyl group, an ethyl group, a butyl group, an isobutyl group, an isoamyl group, a hexyl group, a 2-ethylhexyl group, an octyl group, an isooctyl group, an isononyl group, an isodecyl group, and the like.

On the other hand, other monomers that are optionally used as a copolymerization component include vinyl monomers such as acrylic acid, methacrylic acid, styrene, α-methylstyrene, o-methylstyrene, ρ-methylstyrene, acrylonitrile, and vinyl acetate. can give.

The monomers used to construct the acrylic polymer are:
It is appropriately determined from the viewpoint of compatibility with the acrylic pressure-sensitive adhesive to be compounded. Generally, the same acrylic acid ester as the main monomer constituting the acrylic pressure-sensitive adhesive is used as the main monomer.

The block copolymer used in the present invention is represented by A-B or A-B-A when the block unit composed of polydiorganosiloxane is represented by A and the block unit composed of an acrylic polymer is represented by B. Having a repeating unit of The number average molecular weight is 1
However, the amount is not limited to this.

Preparation of such a block copolymer is, for example, a polydiorganosiloxane having a functional group such as a hydroxyl group at the terminal, and a functional group capable of reacting with the functional group such as a hydroxyl group, a carboxyl group, an isocyanate group, a thiol group at the terminal. It can be carried out by condensation reaction with the acrylic polymer. It can also be prepared by an anionic polymerization method or a group transfer polymerization method in which an acrylic acid ester is polymerized using silyl ketene acetal or the like as an initiator and then polydiorganosiloxane having a methacryloyl group or the like at the terminal is reacted with this.

As a method for obtaining the above-mentioned acrylic polymer having a functional group at the terminal, a polymerization initiator having a functional group, for example, hydrogen peroxide, 4,4′-azobis (4-cyano-1-
(Pentanol) to obtain a polymer having a hydroxyl group at the terminal, 4,4'-azobis (4-cyanovalerianic acid) to obtain a polymer having a carboxyl group at the terminal, or mercaptoethanol, trichloroacetyl Chloride, or using a chain transfer agent such as trichloroacetic acid, a method for obtaining a polymer having a hydroxyl group, an acid chloride group, or a carboxyl group at the terminal, and further an acrylic polymer having the functional group at the terminal, 2,4- Examples thereof include a method of reacting with an excess amount of diisocyanate such as tolylene diisocyanate and methylenebisphenyl isocyanate to obtain a polymer having an isocyanate group at a terminal.

The removable pressure-sensitive adhesive of the present invention is obtained by blending the above block copolymer with an acrylic pressure-sensitive adhesive. The content of the block unit composed of polydiorganosiloxane in the removable pressure-sensitive adhesive is preferably 0.05 to 10% by weight. If the content of the block unit is less than 0.05% by weight, the effect of imparting removability is poor, and if it exceeds 10% by weight, the adhesion to the supporting substrate and the non-staining property to the adherend are poor, which is not preferable.

There is no particular limitation on the acrylic pressure-sensitive adhesive as an object to be mixed with the above block copolymer, and it may be one to which a compounding agent such as a curing agent, which does not cause contamination of the adherend, is added. . An acrylic pressure-sensitive adhesive that can be preferably used is a polymer having a composition in which an alkyl ester of acrylic acid or methacrylic acid accounts for 60% by weight or more as a base polymer and contains 60% by weight or more of this base polymer.

The adhesive of the present invention facilitates re-peeling. Therefore, it is preferably used for a material such as a surface protection material or a masking material for the purpose of preventing scratches during processing or transportation, which needs to be re-peeled after being once attached to an adherend. In that case, the pressure-sensitive adhesive is generally used in a state of being attached to an appropriate supporting substrate such as paper-based, cloth-based, plastic-based, metal foil-based and the like. The adherend to be attached is represented by a metal plate, a plastic plate, a glass plate, a silicon plate or a semiconductor wafer. The pressure-sensitive adhesive can be easily attached to the adherend by a usual method such as a roll pressure method.

EFFECT OF THE INVENTION The removable pressure-sensitive adhesive comprising the acrylic pressure-sensitive adhesive of the present invention contains a silicone / acrylic block copolymer and is therefore excellent in removability. Further, the block copolymer has excellent affinity with the acrylic pressure-sensitive adhesive, is difficult to be separated, and is also excellent in non-staining property to an adherend.

Example Reference Example 1 (Block Copolymer) 70 parts of butyl acrylate (parts by weight, the same applies hereinafter) and 30 parts of butyl methacrylate were added to 4,4′-azobis (4-cyano-1-pentanol) in toluene. 0.5 part (initiator)
And a polymerization treatment in the presence of 1 part of mercaptoethanol (chain transfer agent) to give a hydroxyl group at the terminal number average molecular weight of 1
0,000 acrylic polymers were obtained.

Then, a 40% by weight solution of the acrylic polymer in toluene was added at 40 ° C. containing 4 parts of 2,4-tolylene diisocyanate.
Was added dropwise to 40 parts of a toluene solution of and reacted. The obtained reaction liquid was poured into n-hexane to precipitate a product, which was washed twice with n-hexane and dried to obtain an acrylic polymer having an isocyanate group at the terminal.

Next, 50 parts of polydimethylsiloxane having a number average molecular weight of 5,000 having a hydroxyl group based on a silanol group at one end,
Dibutyltin dilaurate (1 part) was added to 100 parts of toluene, stirred sufficiently and heated to 60 ° C., and the solution was added to the acrylic polymer 100 having an isocyanate group at the end.
A 40 wt% toluene solution containing 1 part was dropped and reacted to obtain a block copolymer.

In this block copolymer, when a block composed of polydimethylsiloxane is represented by A and a block composed of an acrylic polymer is represented by B, a repeating unit represented by AB and a unit represented by ABAA are represented. With a number average molecular weight of 15,000.

Reference Example 2 (Acrylic Adhesive) 65 parts of butyl acrylate, 30 parts of butyl methacrylate, and 5 parts of 2-hydroxyethyl methacrylate were mixed with 0.5 part of 2,2′-azobisisobutyronitrile in toluene. Polymerization treatment was carried out in the presence to obtain a solution of an acrylic copolymer having a number average molecular weight of 50,000.

Example 1 80 parts of the acrylic copolymer of Reference Example 2 (solid content, the same applies hereinafter), 20 parts of the block copolymer of Reference Example 1 and 1 part of a polyisocyanate crosslinking agent were mixed to prepare an adhesive solution. Obtained.
The content of polydimethylsiloxane in the pressure-sensitive adhesive (calculated value, the same applies below) was 6.6% by weight.

Example 2 95 parts of the acrylic copolymer of Reference Example 2, 5 parts of the block copolymer of Reference Example 1, and polyisocyanate crosslinking agent 1
The parts were mixed to obtain an adhesive solution. The content of polydimethylsiloxane in the adhesive is 1.7% by weight.

Example 3 99 parts of the acrylic copolymer of Reference Example 2, 1 part of the block copolymer of Reference Example 1, and polyisocyanate crosslinking agent 1
The parts were mixed to obtain an adhesive solution. The content of polydimethylsiloxane in the adhesive is 0.33% by weight.

Comparative Example 1 An adhesive solution was obtained in the same manner as in Example 1 except that 100 parts of the acrylic copolymer of Reference Example 2 and 1 part of the polyisocyanate cross-linking agent were used and the block copolymer was not used.

Comparative Example 2 Instead of the block copolymer, 3 parts of polydimethylsiloxane (number average molecular weight 5,000), 97 parts of the acrylic copolymer of Reference Example 2 and 1 part of polyisocyanate crosslinking agent were mixed to prepare an adhesive solution. Got The content of polydimethylsiloxane in the adhesive is 3.0% by weight.

Evaluation Test The pressure-sensitive adhesive solutions obtained in Examples and Comparative Examples were applied onto a 25 μm-thick polyester film so that the thickness after drying would be 25 μm, and dried at 100 ° C. for 3 minutes to prepare pressure-sensitive adhesive tapes. The following tests were carried out.

[Adhesive strength] 2kg against stainless steel plate SUS304 at 20 ℃ and 65% RH
The roller of (1) was reciprocated and pressure-bonded, and the 180 degree peeling adhesive force of the adhesive tape left for 20 minutes was measured by an Instron type universal testing machine (20 ° C., 65% RH) under the condition of a pulling speed of 300 mm / min.

[Removability] Adhesive tape pressure-bonded according to the above, 50 ℃ × 65% RH, 50
After being left for 72 hours in an atmosphere of ℃ × 85% RH or 70 ℃ × 65% RH, the adhesive strength was measured according to the above.

[Non-staining] Visually observing the surface of the stainless steel plate after checking the removability, ○ when it is the same as before the adhesive tape was attached, △ when cloudiness was observed, and adhesive (adhesive) residue was observed The evaluation was evaluated as x.

 The results are shown in the table.

The unit of adhesive strength and removability in the table is g / 20mm.
Is.

Claims (4)

(57) [Claims] 1. A removable pressure-sensitive adhesive comprising an acrylic pressure-sensitive adhesive compounded with a block copolymer having a block unit made of polydiorganosiloxane and a block unit made of an acrylic polymer. 2. The block copolymer is AB or A.
A repeating unit represented by -BA (wherein A is a block unit composed of polydiorganosiloxane,
Is a block unit made of an acrylic polymer. The re-peelable pressure-sensitive adhesive according to claim 1, which has a). 3. The removable pressure-sensitive adhesive according to claim 1, wherein the compounding amount of the block copolymer is 0.05 to 10% by weight based on the block unit composed of polydiorganosiloxane. 4. The removable pressure-sensitive adhesive according to claim 1, wherein the block unit composed of polydiorganosiloxane has a number average molecular weight of 1,000 to 50,000.