JPS6121980B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an adhesive composition for pressure-sensitive adhesive tapes or sheets that exhibits excellent adhesive strength to adherends, particularly to adherends made of polyolefin resins such as polyethylene and polypropylene. Recently, pressure-sensitive adhesive tapes and sheets have made remarkable advances in the field of industrial applications, especially the use of double-sided adhesive tapes used for surface-to-surface adhesion, which was traditionally an application field of adhesives. It's typical. 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 pressure-sensitive adhesive tape base material is made of a polyolefin resin such as polyethylene or polypropylene, sufficient adhesion cannot be obtained because the polyolefin resin is nonpolar. In view of the current situation as described above, the present inventors have conducted intensive research and found that a solution-type acrylic copolymer, which is commonly used as a pressure-sensitive adhesive, has a 1/10
By blending a low molecular weight copolymer with an average molecular weight of ~1/100 and no crosslinkable functional groups, this composition has sufficient adhesion to adherends made of polyolefin resin. The present invention was completed based on the knowledge that
The gist is 1. (i) A copolymer mainly composed of an acrylic ester or methacrylic ester whose alkyl group has 4 to 18 carbon atoms and a monomer having a crosslinkable functional group, which is 100 parts by weight of a solvent with an intrinsic viscosity of 0.75 or more at 30°C; (ii) a main component of an acrylic ester or methacrylic ester with an alkyl group having 4 to 18 carbon atoms and containing a crosslinkable functional group; It is a copolymer with no intrinsic viscosity at 30℃ using acetone as a solvent.
10-120 parts by weight of 0.70 or less, (iii) 0.5-120 parts by weight of crosslinking agent
A pressure-sensitive adhesive composition comprising 5 parts by weight of the three components (i), (ii), and (iii). and 2 (i) A copolymer mainly composed of an acrylic ester or methacrylic ester in which the alkyl group has 4 to 18 carbon atoms and a monomer having a crosslinkable functional group, which is prepared using acetone as a solvent. 100 parts by weight of a substance with an intrinsic viscosity of 0.75 or more at 30℃; It is a polymer whose intrinsic viscosity at 30℃ using acetone as a solvent is
10-120 parts by weight of 0.70 or less, (iii) 0.5-120 parts by weight of crosslinking agent
5 parts by weight, (iv) adhesive resin 50 parts by weight or more
A pressure-sensitive adhesive composition characterized by containing four components (i), (ii), (iii), and (iv). The composition that is a combination of component (i) and component (iii) in the present inventions 1 and 2 is a conventional composition for a cross-linked solution-type acrylic adhesive, and the present invention provides a combination of component (i) and (iii). ) is a copolymer mainly composed of the same acrylic monomer as Component (i), but does not contain crosslinkable functional groups.
The gist is to further add a low molecular weight copolymer having an average molecular weight of about 1/10 to 1/100 as component (ii). The reason why the combined use of component (ii) improves the adhesion to adherends, especially to adherends made of polyolefin resin, is that component (ii) has a low molecular weight and However, because it does not have a functional group and is not crosslinked by the crosslinking agent (iii), the critical surface tension is small, so overall it has less wettability to the adherend than a normal solution-type acrylic adhesive. This is thought to be because it is good. In addition, the role of component (iv) in Invention 2 is to maintain the above-mentioned effects obtained by using component (ii) by blending the adhesive resin, while increasing the cohesive force and holding power of the entire composition. In particular, the holding force can be further improved. Component (i) in Inventions 1 and 2 is a higher ester monomer a necessary for imparting adhesive strength, that is, an acrylic ester or methacrylic ester whose alkyl group has 4 to 18 carbon atoms; It consists of a copolymer whose main component is monomer b having a functional group necessary for adjusting adhesive force and cohesive force and imparting crosslinking ability, and higher ester monomer a includes butyl acrylate, acrylic Examples include 2-ethylhexyl acid and lauryl methacrylate, and one or more of these may be used. As monomer b having a functional group, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, acrylic acid 2
Monomers with alcoholic hydroxyl groups such as hydroxyethyl, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, N-methylol acrylamide, and epoxy groups such as glycidyl acrylate and glycidyl methacrylate. One or more types of monomers belonging to the three groups having the following are used. In addition, component (i) further contains a type of acrylic ester or methacrylic ester with an alkyl group having 1 to 3 carbon atoms, vinyl acetate, or vinyl propionate as component c in order to adjust the adhesive force and cohesive force. Alternatively, two or more types may be used, and the appropriate weight ratio of each monomer component in component (i) is within the range of 70 to 99% by weight for a. and 1 to 10% by weight for b. , and when c is added, each is used within a range of 20% by weight or less. These monomer components are then copolymerized using the usual solution weight method to form the component.
(i), and the solvent used is ethyl acetate, and the polymerization initiator is generally benzoyl peroxide, acetyl peroxide, azobisisobutyronitrile, etc. The intrinsic viscosity of the thus obtained copolymer at 30°C using acetone as a solvent is
It falls within the range of 0.75 or higher. Component (ii) in Inventions 1 and 2 is a solution of the monomer components excluding monomers having a functional group from the monomer group forming component (i), as in component (i). It is obtained by a polymerization method, but the average molecular weight is 1/1 that of component (i).
It must be about 10 to 1/100 times lower, and in order to obtain such a low molecular weight, it is necessary to use a solvent with a large chain transfer effect such as carbon tetrachloride during polymerization, or to use a conventional solvent such as ethyl acetate. It is sufficient to use a chain transfer agent such as mercaptans, or to use a polymerization initiator in an amount 5 to 20 times that of component (i). The intrinsic viscosity is within the range of 0.70 or less. When the crosslinkable functional group of component (i) is, for example, a carboxyl group or an alcoholic hydroxyl group, polyfunctional isocyanates are recommended as component (iii) in Inventions 1 and 2, and typical examples include trifunctional isocyanates. An example is an adduct of three molecules of diisocyanate and one molecule of trimethylolpropane, and other polyfunctional isocyanates with similar structures and etherified methylolmelamines may also be used. When the functional group is an epoxy group, it is appropriately selected from aliphatic amines, aromatic diamines, modified amines, polyamide resins, and heterocyclic diamines. Component (iv) of the present invention 2 may be any adhesive resin that has good compatibility with the other components (i) and (ii), but phenolic resins are usually preferably used. Specific examples include phenol/formalin resin, cresol/formalin resin, 100% phenolic resin, natural resin-modified phenolic resin, and styrene-modified phenolic resin, and the higher the softening temperature, the better the adhesive strength of the composition. This is preferable because the holding force is improved. The blending ratio of each of the above components used in Inventions 1 and 2 is as follows: component (ii) to 100 parts by weight of component (i).
is used in an amount of 10 to 120 parts by weight, component (iii) is used in an amount of 0.5 to 5 parts by weight, and the component in Invention 2
(iv) must be less than 50 parts by weight and component (ii)
When the amount of 120 parts by weight is less than 10 parts by weight, the role played by the low molecular weight acrylic copolymer in the adhesive composition, that is, sufficient adhesion to the surface of the nonpolar adherend cannot be obtained; If the amount exceeds 1 part by weight, both the cohesive force and the holding force decrease. Also, component (iii)
When the amount is less than 0.5 parts by weight, the crosslinkable functional groups in component (i) cannot be sufficiently crosslinked, and the necessary cohesive force cannot be obtained.On the other hand, when it exceeds 5 parts by weight, the adhesive composition If the object becomes too hard and the necessary adhesive strength cannot be obtained, and if component (iv) exceeds 50 parts by weight,
The necessary cohesive force and holding power cannot be obtained. Therefore, in order to produce the pressure-sensitive adhesive compositions of the present inventions 1 and 2, it is sufficient to simply put a predetermined amount of each component into a container and stir and mix to form a uniform mixture. In the present invention, known additives can be appropriately added to the pressure-sensitive adhesive composition thus obtained, and it can be used in the same manner as conventional additives. The pressure-sensitive adhesive composition of the present invention can be applied to a substrate by a commonly used coating method using a roll or knife, and there are no particular limitations on the material of the substrate. Not done. The pressure-sensitive adhesive composition of the present invention 1 contains an acrylic copolymer used in ordinary pressure-sensitive adhesives and the same acrylic monomer as the copolymer as a main component,
Since the copolymer has a low molecular weight with an average molecular weight of about 1/10 to 1/100 of the copolymer and does not contain crosslinking functionality,
When this is used as a pressure-sensitive adhesive for adhesive products such as pressure-sensitive adhesive tapes or sheets, the critical surface tension of the adhesive is smaller than that of ordinary acrylic pressure-sensitive adhesives, and the adherend is made of polyolefin. Even when the adhesive is made of a non-polar material such as a non-polar resin, it can wet the adherend well and therefore provide good adhesive strength. In addition, since the pressure-sensitive adhesive composition of the present invention 2 further includes an adhesive resin in the pressure-sensitive adhesive composition of the present invention 1, the adhesive strength and holding power of the entire composition, especially the holding power, are improved. Further improvements can be made to achieve a good balance between the two, and it is possible to obtain products that exhibit excellent adhesion not only to non-polar adherends but also to general articles such as steel. This will be explained below with reference to examples. It should be noted that all references to "middle part" in Examples and Comparative Examples refer to parts by weight. Example 1 100 parts of ethyl acetate was placed in a reactor, heated while stirring to boiling, and 60 parts of 2-ethylhexyl acrylate, 32.5 parts of butyl acrylate, 5 parts of ethyl acrylate, acrylic acid
First of a mixture of 2.5 parts benzoyl peroxide and 0.12 parts benzoyl peroxide.
Add 1/4 amount at a time, and add the same amount every hour while stirring, heating, and refluxing to proceed with polymerization. During this time, the temperature in the reactor gradually increases and reaches 95° C. at the end of the last addition. After the last addition was completed, the reaction was continued in the same manner for another 3 hours until completion. After that, it is cooled to room temperature. The thus obtained component (i) had a solid content concentration of 49% and a viscosity of
20000 centipoise, 30℃ with acetone as solvent
The intrinsic viscosity was 0.89. In addition, in another reactor, 150 parts of carbon tetrachloride, 60 parts of 2-ethylhexyl acrylate, and 35 parts of butyl acrylate were added.
parts, ethyl acrylate 5 parts, benzoyl peroxide 2 parts
1 part, heated to boiling while stirring, continued stirring and refluxing in this state for 12 hours to complete polymerization, and then cooled to room temperature. The thus obtained component (ii) had a solid concentration of 39%, a viscosity of 1500 centipoise, and an intrinsic viscosity at 30°C using acetone as a solvent.
It was a copolymer with a low molecular weight of 0.49. Next, take 100 parts of the above component (i) and 44 parts of component (ii),
To this, 31 parts of a 40% methyl ethyl ketone solution of terpene-modified phenolic resin was mixed as component (iv), and 1.31 parts of trifunctional isocyanate was further added as component (iii), and the mixture was stirred and mixed until the solid content was approximately 45% of the composition of invention 2 was obtained. Next, this composition was applied to both sides of a base material made of nonwoven fabric with a width of 15 mm so that the adhesive thickness was 65 μm on one side to obtain a double-sided adhesive tape. Example 2 A composition of the present invention 1 was obtained in the same manner as in Example 1, except that the terpene-modified phenol resin as component (iv) in Example 1 was not used, and a double-sided adhesive tape was obtained. Comparative Example 1 A double-sided adhesive tape was obtained in the same manner as in Example 1 except that component (ii) in Example 1 was not used. Comparative Example 2 The amount of component (ii) in Example 1 was changed to 132 parts,
A double-sided adhesive tape was obtained in the same manner as in Example 1, except that the amount of component (iv) was changed to 92 parts. Comparative Example 3 A double-sided adhesive tape was obtained in the same manner as in Example 1, except that the blend of component (iv) in Example 1 was changed to 92 parts. Comparative Example 4 A double-sided adhesive tape was obtained in the same manner as in Example 1, except that component (iii) in Example 1 was not used. Comparative Example 5 A double-sided adhesive tape was obtained in the same manner as in Example 1, except that component (ii) and component (iv) in Example 1 were not used. Example 3 100 parts of ethyl acetate was charged into a reactor, and Example 1
In the same manner as above, a mixture of 20 parts of lauryl methacrylate, 77 parts of butyl acrylate, 3 parts of methacrylic acid, and 0.12 parts of benzoyl peroxide was added to conduct polymerization, and the solid content concentration was 48%, the viscosity was 12,000 centipoise, and acetone was used as the solvent. Component (i) having an intrinsic viscosity of 0.91 at 30°C was obtained. In addition, in another reactor, 110 parts of ethyl acetate, 40 parts of methyl ethyl ketone, 20 parts of lauryl methacrylate,
80 parts of butyl acrylate, 0.01 part of tertiary butyl mercaptan, and 1.0 part of benzoyl peroxide were charged, and polymerization was carried out in the same manner as in Example 1 until the solid content concentration was 38.
%, a viscosity of 1400 centipoise, and an intrinsic viscosity of 0.48 at 30°C using acetone as a solvent was obtained. Next, take 100 parts of the above component (i) and 38 parts of component (ii),
24 parts of a 40% methyl ethyl ketone solution of 100% phenolic resin (component (iv)) was mixed with this, and then component (iii)
1.53 parts of a trifunctional isocyanate was added thereto, and the mixture was stirred and mixed until homogeneous to obtain a composition of the present invention 2 having a solid content concentration of about 45%. Next, a double-sided adhesive tape was obtained using this composition in the same manner as in Example 1. Example 4 A composition of the present invention 1 was obtained in the same manner as in Example 3, except that the 100% phenolic resin as component (iv) in Example 3 was not used, and a double-sided adhesive tape was obtained. Comparative Example 6 A double-sided adhesive tape was obtained in the same manner as in Example 3, except that component (ii) in Example 3 was not used. Comparative Example 7 The amount of component (ii) in Example 3 was changed to 132 parts,
A double-sided adhesive tape was obtained in the same manner as in Example 3, except that the amount of component (iv) was changed to 92 parts. Comparative Example 8 A double-sided adhesive tape was obtained in the same manner as in Example 3, except that the amount of component (iv) in Example 3 was changed to 92 parts. Comparative Example 9 A double-sided adhesive tape was obtained in the same manner as in Example 3, except that component (iii) in Example 3 was not used. Comparative Example 10 A double-sided adhesive tape was obtained in the same manner as in Example 3, except that component (ii) and component (iv) in Example 3 were not used. Comparative Example 11 100 parts of ethyl acetate was charged into a reactor, and Example 1
60 parts of 2-ethylhexyl acrylate in the same manner as
Butyl acrylate 32.5 parts, ethyl acrylate 5 parts
2.5 parts of acrylic acid and 1.5 parts of benzoyl peroxide were added to carry out polymerization, and the solid content concentration was 48.5 parts.
%, a viscosity of 8500 centipoise, and an intrinsic viscosity of 0.53 at 30°C using acetone as a solvent was obtained. A double-sided adhesive tape was obtained in the same manner as in Example 1 using the obtained component (i) and component (ii) in Example 1. Comparative Example 12 A double-sided adhesive tape was obtained in the same manner as in Comparative Example 11, except that the terpene-modified phenol resin as component (iv) in Comparative Example 11 was not used. Comparative Example 13 A reactor was charged with 150 parts of carbon tetrachloride, 60 parts of 2-ethylhexyl acrylate, 35 parts of butyl acrylate, 5 parts of ethyl acrylate, and 0.2 parts of benzoyl peroxide, and polymerized in the same manner as in Example 1 to form a solid. Min concentration 39
%, a viscosity of 18,000 centipoise, and an intrinsic viscosity of 0.78 at 30°C using acetone as a solvent was obtained. A double-sided adhesive tape was obtained in the same manner as in Example 1 using the obtained component (ii) and component (i) in Example 1. Comparative Example 14 A double-sided adhesive tape was obtained in the same manner as in Comparative Example 13, except that the terpene-modified phenol resin as component (iv) in Comparative Example 13 was not used. Comparative Example 15 A double-sided adhesive tape was obtained in the same manner as in Example 1 using component (i) in Comparative Example 11 and component (ii) in Comparative Example 13. Comparative Example 16 A double-sided adhesive tape was obtained in the same manner as in Comparative Example 15, except that the terpene-modified phenol resin as component (iv) in Comparative Example 15 was not used. The solid content ratio of the ingredients of the adhesive composition used in the double-sided adhesive tapes obtained in the above Examples and Comparative Examples and the performance of the tapes are shown in Tables 1, 2, and 3. . The measurements in these tables were made under the same conditions after each double-sided adhesive tape was left at 20° C. and 60% relative temperature for 72 hours.

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[Table] Looking at the above tables, it can be seen that the adhesive tapes using the pressure-sensitive adhesive composition of the present invention 1, that is, those of Examples 2 and 4, have particularly excellent adhesive strength to adherends made of polyolefin resin. and holding force, and the present invention 2
Adhesive tapes using the pressure-sensitive adhesive composition of Example 1 and 3 were found to have significantly improved holding power compared to those of Examples 2 and 4, and had a good balance between adhesive force and holding force. It can be seen that even the peeled stainless steel plate has physical properties comparable to those of each comparative example.

Claims (1)

[Scope of Claims] 1 (i) A copolymer whose main components are an acrylic ester or methacrylic ester whose alkyl group has 4 to 18 carbon atoms and a monomer having a crosslinkable functional group; , 100 parts by weight of a substance with an intrinsic viscosity of 0.75 or more at 30°C using acetone as a solvent, (ii) a crosslinkable functional material whose main component is an acrylic ester or methacrylic ester whose alkyl group has 4 to 18 carbon atoms; Copolymers that do not contain groups and have an intrinsic viscosity of 0.70 or less at 30°C using acetone as a solvent10~
(i) 120 parts by weight, (iii) 0.5 to 5 parts by weight of a crosslinking agent;
A pressure-sensitive adhesive composition comprising three components (ii) and (iii). 2 (i) A copolymer whose main components are an acrylic ester or methacrylic ester whose alkyl group has 4 to 18 carbon atoms and a monomer having a crosslinkable functional group, and uses acetone as a solvent. 100 parts by weight of a product with an intrinsic viscosity of 0.75 or more at 30°C, (ii) a copolymer mainly composed of acrylic ester or methacrylic ester with an alkyl group having 4 to 18 carbon atoms and containing no crosslinkable functional group. A combination with an intrinsic viscosity of 0.70 or less at 30℃ using acetone as a solvent10~
120 parts by weight, (iii) 0.5 to 5 parts by weight of cross-linking agent, and (iv) 50 parts by weight of adhesive resin. Characteristic pressure-sensitive adhesive composition.