JPS5818958B2 - pressure sensitive adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a pressure-sensitive adhesive tape in which the material of the adherend of the pressure-sensitive adhesive tape or the base material of the pressure-sensitive adhesive tape is a soft vinyl chloride resin containing a low-molecular plasticizer. The present invention relates to a pressure sensitive adhesive composition suitable for use as a tape adhesive.

Recently, pressure-sensitive adhesive tapes have made remarkable advances in the field of industrial applications, and a typical example of this is the use of double-sided adhesive tapes, which are used for surface-to-surface adhesion, which was traditionally an application field for adhesives. It is something.

The reason for this is the excellent labor-saving and pollution-free nature of pressure-sensitive adhesive tapes.

However, when the material of the adherend or the base material of the pressure-sensitive adhesive tape is made of a soft vinyl chloride resin containing a low-molecular plasticizer, the low-molecular plasticizer may be transferred to the adhesive side over time after pasting. Leaching occurs, leading to softening of the adhesive and a decrease in adhesive strength.

The tendency to overlap is particularly noticeable in the case of rubber-based adhesives, but
This is true even for solution-type acrylic adhesives that have relatively good cohesive strength; for example, in the case of a non-crosslinked solution-type acrylic adhesive, the adhesive softens, and in the case of a crosslinked type, the adhesive softens dramatically. was smaller, but a decrease in adhesive strength was unavoidable.

As a result of intensive research to resolve the drawbacks of the cross-linked solution-type acrylic adhesives, the present inventors have developed a cross-linked acrylonitrile-butadiene copolymer rubber that originally has good adhesion to sheets made of soft vinyl chloride resin. It has been discovered that when a composition obtained by adding a small amount to a type of solution-type acrylic adhesive is used as an adhesive, the adhesive does not soften over time and can maintain its strong adhesive strength. The present invention has been completed, and the gist thereof is 80 to 96 mol% of an acrylic ester or methacrylic ester whose alkyl group has 3 to 10 carbon atoms and 4 to 20 mol % of a monomer having a polar group. % and a crosslinking agent capable of crosslinking the polar group to a sticky copolymer solution copolymerized in an organic solvent;
Based on 100 parts by weight of the adhesive copolymer, the main components are acrylonitrile and butadiene, and the acrylonitrile content is 1.
5 to 40 parts by weight of a copolymer rubber in an amount of 5 to 45 mol % is added, and the above polar group is crosslinked.

The acrylic ester or methacrylic ester used in the present invention has an alkyl group having 3 to 10 carbon atoms.
The reason for this is that those with less than 3 carbon atoms have low adhesiveness, while those with more than 10 are highly sticky and have poor adhesiveness.For example, Examples include butyl acrylate, 2-ethylhexyl acrylate, and the like.

The monomer used in the present invention can be copolymerized with the above-mentioned acrylic ester or methacrylic ester, has a polar group, and has the effect of improving adhesiveness to the tape base material. For example, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, 2-
Examples include hydroxymethyl methacrylate.

In the present invention, the acrylic ester or methacrylic ester and the monomer are copolymerized to form an adhesive copolymer, and the content of the acrylic ester or methacrylic ester in the copolymer is 80 to 80%. 96
The monomer content is 4 to 20 mol%.

The reason why the content of acrylic ester or methacrylic ester is limited to 80 to 96 mol% is that if it is less than 80 mol%, sufficient cohesive force as a pressure-sensitive adhesive composition cannot be obtained; This is because if the amount exceeds mol%, the adhesiveness deteriorates.

The above copolymerization is carried out in an organic solvent, for example, by adding the above acrylic ester or methacrylic ester and the monomer to benzoyl peroxide, azobisisobutyronitrile, etc. in an organic solvent such as toluene, ethyl acetate, or methyl ethyl ketone. It may be supplied together with a polymerization initiator and heated.

In the present invention, the above-mentioned adhesive copolymer is crosslinked by a crosslinking agent, and the crosslinking agent is a polyfunctional isocyanate such as tolylene diisocyanate, diphenylmethane diisocyanate, etc. Examples include isocyanate-based crosslinking agents and melamine-based crosslinking agents.

Although the crosslinking ratio is not particularly limited, it is preferable that 10 to 50 mol% of the polar groups of the copolymer be crosslinked.

Further, crosslinking is preferably carried out by adding and mixing a crosslinking agent together with the copolymer and the copolymer rubber described below.

The copolymer rubber containing acrylonitrile and butadiene as main components used in the present invention has an acrylonitrile content of 15 to 45 mol%, preferably an acrylonitrile content of 30 mol% to 40 mol%, and an acrylonitrile content of 15 to 45 mol%. If the amount is less than 45 mol%, the adhesive composition will not have plasticizer resistance, and if the amount is less than 45 mol%, the adhesive composition will not have plasticizer resistance.
If it exceeds 100%, the initial tackiness of the pressure-sensitive adhesive composition will be poor.

In addition, the copolymer rubber containing acrylonitrile and butadiene as main components used in the present invention may include a so-called carboxyl-modified copolymer rubber in which a small amount of a monomer having a carboxyl group, such as acrylic acid or methacrylic acid, is copolymerized. is also used.

The adhesive copolymer and copolymer rubber used in the present invention are used in a ratio of 5 to 40 parts by weight to 100 parts by weight of the former, and 10 to 20 parts by weight of the latter. Preferably, if the amount of the copolymer rubber is less than 5 parts by weight, the pressure-sensitive adhesive composition will not have plasticizer resistance, and if it exceeds 40 parts by weight, the initial tackiness of the pressure-sensitive adhesive composition will deteriorate.

A general method for producing the pressure-sensitive adhesive composition of the present invention is to prepare a solution of copolymer rubber in an organic solvent such as methyl ethyl ketone having a concentration of 10 to 20%, and then add the adhesive copolymer to an organic solvent such as methyl ethyl ketone. It may be added and mixed into the solution.

In the present invention, known additives can be appropriately added to the pressure-sensitive adhesive composition thus obtained.

The pressure-sensitive adhesive composition of the present invention can be applied to a substrate by a commonly used coating method such as a roll coater or a knife coater. Not only soft vinyl chloride resin containing a low-molecular plasticizer, but also various other synthetic resins, paper, cloth, etc. can be suitably used.

The composition of the pressure-sensitive adhesive composition of the present invention is as described above, and contains 100 parts by weight of a cross-linked solution type acrylic adhesive, acrylonitrile and butadiene as main components, and has an acrylonitrile content of 15 to 45 mol%. Copolymer rubber 5
Since it contains ~40 parts by weight, when used as an adhesive for adhesive products such as adhesive tapes or sheets, the adherend or the base material of the adhesive product itself is soft vinyl chloride containing a low-molecular plasticizer. Even if it is made of resin, whether the low-molecular plasticizer leaches into the adhesive side at all over time after pasting.
Or even if there is, it is possible to prevent the softening of the adhesive or the decrease in adhesive strength to a very small extent.

This will be explained below with reference to examples.

In addition, all "parts" in the examples mean "parts by weight."

Example 1 150 parts of ethyl acetate was charged into a reactor, heated while stirring to reach the boiling point, kept under reflux, and mixed with 97 parts of butyl acrylate, 3 parts of acrylic acid, and 0.1 part of benzoyl peroxide.
Add 115 parts of the mixture of 2 parts, continue stirring and refluxing, and after 1 hour have passed, add the remaining 115 parts. From then on, add the same amount every hour, and continue stirring and refluxing to carry out copolymerization. After the final addition was completed, the reaction was allowed to proceed in the same manner for 8 hours, and then cooled to room temperature to obtain a copolymer composition.

The concentration of copolymer in the composition was 38%.

100 parts of this copolymer composition was added with acrylonitrile-butadiene copolymer rubber (Nibole 1041, manufactured by Nippon Zeon Co., Ltd.).
25 parts of a 15% methyl ethyl ketone solution containing L, acrylonitrile content 41 mol%) and 1.63 parts of a crosslinking agent (Corone L, manufactured by Nippon Polyurethane Co., Ltd.) were added, stirred, and mixed uniformly to form a pressure-sensitive adhesive composition. Obtained.

The blending ratio of the adhesive copolymer and copolymer rubber in the obtained pressure-sensitive adhesive composition was 100:10, and the amount of the crosslinking agent added was 3% of the carboxyl groups possessed by the adhesive copolymer.
It is equivalent to 5 mol%.

Next, this composition was applied to both sides of an adhesive tape base material made of nonwoven fabric with a width of 15 mm so that the total thickness was 125 mm, and dried to obtain a double-sided adhesive tape.

Example 2 A pressure-sensitive adhesive was prepared in the same manner as in Example 1, except that 38 parts of a 15% methyl ethyl ketone solution of Nipol 1072 (manufactured by Nippon Zeon, carboxyl modified type, acrylonitrile content 27 mol%) was used as the acrylonitrile-butadiene copolymer rubber. A drug composition was obtained.

The blending ratio of the adhesive copolymer and copolymer rubber in the obtained composition was 100:IQ, and the amount of crosslinking agent added was equivalent to 35 mol% of the carboxyl groups possessed by the adhesive copolymer. It is.

Next, a double-sided adhesive tape was obtained in the same manner as in Example 1 using this composition.

Comparative Example A double-sided adhesive tape was obtained in the same manner as in Example 1, except that acrylonitrile-butadiene copolymer rubber was not used as a component of the pressure-sensitive adhesive composition.

The performance of the above double-sided adhesive tape is shown in the table below.

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

Note 1 The SP adhesion strength in the table above is determined by pasting the sample on a stainless steel plate and attaching it to a 300mm1 plate at a 180 degree angle after 15 minutes.
Indicates the strength when peeled at a speed of 1 minute.

Note 2: The tack in the table above is based on the J, Dow method.

Note 3: The holding force in the table above is determined by pasting the sample on a stainless steel plate so that the dimensions of the pasting surface are 15 mm in width and 10 m in length, fixing the other end of the stainless steel plate,
A 5001 weight is hung from the other end of the sample, and the time required for the sample to fall together with the weight due to adhesive failure between the stainless steel plate and the sample or cohesive failure within the adhesive layer is shown.

Note 4 In the above table, the normal peel force, peel force after aging, normal holding force, and holding force after aging are all tests for plasticizer resistance, and all of them are based on polyamide with an average degree of polymerization of 1100 as the adherend. A soft vinyl chloride resin sheet with a thickness of 3 mm and a smooth surface was used, which was made of 100 parts by weight of vinyl chloride, 80 parts of dioctyl phthalate, and an appropriate amount of a stabilizer.

(1) Normal peel strength indicates the strength when a sample is attached to the adherend and after 3 hours has passed, it is peeled off at an angle of 180 degrees at a speed of 300 mm/min.

(11) Peeling force after aging is determined by applying a bonded sample with normal peeling force to an air chamber at 70°C for 3 days and 7 days, and then leaving it in a measurement room for 24 hours. It shows the strength when peeled at an angle of 300 mm per minute.

(iiD Normal holding power is determined by pasting a sample on one end of the above adherend so that the dimensions of the pasting surface are 15 mm in width and 10 mm in length, fixing the other end of the adherend, and 5001 at the end
The time required for a sample to fall with the weight due to adhesive failure between the adherend and sample or cohesive failure within the adhesive layer is shown.

OV) The post-aging retention strength was measured in the same manner as the normal retention strength (111) by treating the sample in the same manner as for the post-aging peel strength in (1i) above.

Note 5 The measurements in Notes 1 to 4 above were performed with a 25 μm thick polyester film attached to one surface of the sample in all measurements except for tack.

Note 6: When measuring SP adhesive strength, normal peel strength, and peel strength after aging, the failure types of peeling were all normal peeling with no adhesive remaining on the adherend.

In addition, the type of failure caused by falling during the measurement of holding power, normal holding power, and holding power after aging was cohesive failure, except for the comparative example in which the holding force after aging was adhesive failure.

In the samples used for each of the above measurements, especially the samples for peel strength after aging and retention strength after aging, no softening of the adhesive due to leaching of the low molecular plasticizer from the adherend to the adhesive layer of the sample was observed. As is clear from the above table, the examples using the pressure-sensitive adhesive composition of the present invention have significantly higher peel strength and retention strength after aging than the comparative example using only acrylic adhesive. It can be seen that it is excellent.

Claims (1)

[Claims] 1 A sticky copolymer obtained by copolymerizing 80 to 96 mol% of an acrylic ester or methacrylic ester with an alkyl group having 3 to 10 carbon atoms and 4 to 20 mol% of a monomer having a polar group in an organic solvent. In the solution, 5 to 40 parts by weight of a copolymer rubber containing acrylonitrile and butadiene as main components and having an acrylonitrile content of 15 to 45 mol% is added to 100 parts by weight of the adhesive copolymer and a crosslinking agent capable of crosslinking the polar groups. A pressure-sensitive adhesive composition characterized in that the above-mentioned polar group is crosslinked.