JPS6032873A - Pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:The titled composition having high cohesive force and improved tack, obtained by blending an acrylic emulsion type pressure-sensitive adhesive containing a crosslinkable functional group with a melamine resin as a crosslinking agent and an aziridinyl compound in a specific ratio. CONSTITUTION:100pts.wt. acrylic emulsion type pressure-sensitive adhesive containing a crosslinkable functional group [preferably one obtained by copolymerizing a (meth)acrylic acid alkyl ester such as n-butyl acrylate, etc. with a crosslinkable functional group-containing monomer such as acrylic acid, etc. in an emulsion type] is blended with 0.1-10pts.wt. melamine resin (e.g., methylolmelamine, etc.) and 0.001-5pts.wt. aziridinyl compound [e.g., 1,1'-(methylene-di-p- phenylene)-bis-3,3-aziridinylurea, etc.] as a crosslinking agent, to give the desired composition. A ratio of the melamine resin/the aziridinyl compound is especially preferably 0.05-100.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an emulsion-type pressure-sensitive adhesive composition that exhibits high cohesive strength and excellent adhesive strength. More specifically, the present invention relates to a pressure-sensitive adhesive composition in which an acrylic emulsion-type pressure-sensitive adhesive having a crosslinkable functional group is blended with a melamine resin and an aziridinyl compound as a crosslinking agent.

Conventionally, acrylic pressure-sensitive adhesives include monomers containing (meth)acrylic acid alkyl ester as the main monomer, monomers having carboxyl groups, amide groups, hydroxyl groups, etc., vinyl acetate, Copolymerized products of one or more monomers such as acrylonitrile and styrene are known, but uncrosslinked products generally have poor cohesiveness and temperature-sensitive properties.
Various crosslinking methods have been used to improve this problem.

For example, there are pressure-sensitive adhesives in which a pressure-sensitive adhesive component having a carboxyl group is crosslinked with isocyanates, melamine resins, epoxy resins, metal salts, etc. Effective. but,
Crosslinking with isocyanates, melamine resins, and epoxy resins requires a long curing time at high temperatures because the crosslinking speed is slow.

Furthermore, since the reactivity of the above crosslinking agents is low, unreacted substances do not remain (when pressure-sensitive adhesive tapes are manufactured, adhesive strength and adhesive strength may decrease due to changes over time, and isocyanates are difficult to react with moisture). The reactivity was short, and melamine resin crosslinking had the disadvantage of poor cohesiveness at around 100°C.Furthermore, metal salt crosslinking has a relatively fast reaction, but it raises the glass transition temperature of the pressure-sensitive adhesive. This had the disadvantage of causing a decrease in adhesive strength and adhesive strength.

The present inventors have conducted repeated research to eliminate the above drawbacks all at once, and have found that a pressure-sensitive adhesive composition obtained by using a melamine resin and an aziridinyl compound together in a specific ratio as a crosslinking agent has excellent adhesive properties. The present invention was achieved by discovering that the crosslinking agent has excellent temperature-sensitive properties and exhibits unique effects that were not exhibited when the above-mentioned crosslinking agents were used individually.

That is, the pressure-sensitive adhesive composition of the present invention is an acrylic emulsion-type pressure-sensitive adhesive having a crosslinkable functional group with a solid content of 1
00 parts by weight, melamine resin 0.1 to 1 as a crosslinking agent
0 parts by weight and 0.001 to 5 parts by weight of an aziridinyl compound.

The acrylic emulsion-type pressure-sensitive adhesive having a crosslinkable functional group used in the present invention coexists in an emulsion type with a main component consisting of an alkyl (meth)acrylate ester and a monomer having a crosslinkable functional group. It is a polymerized copolymer.

The main component (meth)acrylic acid alkyl ester is a monomer whose alkyl group has 2 to 15 carbon atoms, such as (meth)acrylic acid ethyl ester, (meth)acrylic acid butyl ester, hexyl (meth)acrylate. ester,
Examples include (meth)acrylic acid octyl ester, (meth)acrylic acid nonyl ester, and (meth)acrylic acid dodecyl ester, and monomers having linear or branched side chain alkyl groups can also be used. Two or more of the above ALM bodies may be used in combination depending on the purpose.

Monomers having a crosslinkable functional group to be copolymerized with the above main component monomers include monomers having a carboxyl group such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid; Monomers having a hydroxyl group, such as hydroxyethyl meth)acrylate, hydroxypropyl acrylate (meth)acrylate,
Monomers having an amide group or an amino group such as acrylamide, methacrylamide, N-methylolacrylamide, (meth)acrylic acid dimethylaminoethyl ester, (meth)acrylic acid diethylaminoethyl ester,
Examples include monomers having a glycidyl group such as (meth)acrylic acid glycidyl ester. The copolymerization ratio of these monomers having crosslinkable functional groups is preferably in the range of 0.5 to 20% by weight in the acrylic pressure-sensitive adhesive component.

Furthermore, for the purpose of imparting adhesive properties such as adhesive force and cohesive force, monomers other than those mentioned above, such as (meth)acrylic acid methyl ester, (meth)acrylic acid stearyl ester, etc., are used. If necessary, it is also possible to copolymerize (meth)acrylic acid alkyl esters, vinyl acetate, vinyl propionate, acrylonitrile, styrene, (meth)acrylic acid alkoxyalkyl esters, vinyl alkyl ethers, etc. outside the range of 15. It is.

The copolymerization ratio of these monomers is preferably in the range of 90 to 20% by weight of the acrylic pressure-sensitive adhesive component.

The method for producing the acrylic emulsion type pressure-sensitive adhesive having a crosslinkable functional group used in the present invention is not particularly limited as long as it is a commonly performed emulsion polymerization. Anionic surfactants such as alkylnaphthalene sulfonates, fatty acid salts, higher alcohol sulfate ester salts, dialkyl sulfosuccinates, alkyl phosphate salts, and polyoxyethylene sulfate salts may be used alone or in combination with polyoxyethylene alkyl ether, polyoxy Using a nonionic surfactant such as ethylene fatty acid ester,
Alternatively, a nonionic surfactant alone can be used. In addition, as a polymerization initiator, persulfates such as potassium persulfate and sodium persulfate, hydrogen peroxide, perboric acid, I.
Also used are water-soluble azo compounds such as C. In order to adjust the molecular weight of the pressure-sensitive adhesive obtained by emulsion polymerization, chain transfer agents that easily cause hydrogen abstraction reactions, such as mercaptans such as lauryl mercaptan, mercaptoacetic acid, and 2-hydroxyethanethiol, and carbon tetrachloride, etc. May be added.

Melamine-based resins used as crosslinking agents in the present invention include methylolated melamine, which is an initial condensation product of melamine and formaldehyde, alkyl etherified melamine, which is obtained by reacting the methylolated melamine with alcohol, and melamine-urea cocondensation. Examples include alkyl etherified methylol group-containing urea-formaldehyde initial condensate, and guanamine resin, and one or more of these may be used in combination.

Furthermore, the aziridinyl compound used in the present invention is a compound having at least two aziridine rings in one molecule, for example, 1.1'-(methylene-di-p-phenylene)-bis-3,3- aziridinyl urea, 1.1
'-(hexamethylene)-bis-3,3-aziridinyl urea, ethylene bis-(2-aziridinylpropionate), tris(1-aziridinyl)bosphine oxide, 2,4.6-)riaziridinyl-L3, 5-1
-Ryazine, trimethylolpropane-tris-(2-
aziridinyl propionate), etc., and one or more of these may be used in combination.

If the melamine resin and aziridinyl compound are water-soluble, they can be used as a single substance, or if they are insoluble in water, they can be dissolved in a solvent such as 'H2t alcohols, acetone, or dimethylformamide. Added to emulsion type pressure sensitive adhesives. The crosslinking agent component contains melamine resin in an amount of 0.00 parts by weight based on 100 parts by weight of the solid content of the pressure-sensitive adhesive. 1 to 10 parts by weight, and 0.1 to 10 parts by weight of the aziridinyl compound.
0.001 to 5 parts by weight, and optimally the ratio of melamine resin/aziridinyl compound is 0.05 to 100.
A range of is desirable. When the ratio is 0.05 or less, the desired properties can be obtained, but the influence of the aziridinyl compound is strong, and the temperature-sensitive properties may be slightly inferior depending on the type of main monomer. If the ratio is 100 or more, contrary to the above, the influence of the melamine resin is strong, and the adhesive properties may tend to change slightly over time.

Additionally, additives such as tackifiers, fillers, colorants, thickeners, and antifoaming agents for suppressing foaming generated during coating may be added as required by trial decision.

Due to the combined effect of the melamine resin and the aziridinyl compound, the pressure-sensitive adhesive composition of the present invention can be crosslinked by heat drying to an appropriate degree, which could not be achieved by crosslinking each alone, resulting in a balance between cohesive force and adhesive force. The object of the present invention is to provide a pressure-sensitive adhesive layer which has good properties, shows little change in these properties over time, and has excellent temperature-sensitive properties at low and high temperatures. In particular, when combined addition is used, the allowable range of addition amount is greatly expanded.
Since the desired reproducibility of the degree of crosslinking of the pressure-sensitive adhesive composition has been improved, when it is made into a pressure-sensitive adhesive tape, there is also the effect that variations in adhesive properties between products are eliminated.

Examples of the present invention will be specifically described below, but the present invention is not limited thereto and can be applied in various ways without departing from the technical idea. Furthermore, all parts in the examples mean parts by weight. In addition, adhesive strength,
The following measurement methods were used for the holding force and adhesive force.

<Adhesive strength> 14 tapes with a width of 201 were bonded to a stainless steel plate of SUS-304 by making one reciprocation with a 2 kg roller.
Peeling angle of 180 degrees at each measurement temperature, 30c
Adhesive strength when peeled off at a speed of +n/min (g/20
It is shown in the value of the dragon width).

<Holding force> A sample tape is pasted on a Bakelite board with an area of 10 dragon widths x 20 fin lengths, and a load of 500 g is applied vertically to one end of the sample tape in an atmosphere of 80°C, causing the sample tape pieces to fall due to cohesive failure. The time was measured.

<Adhesive strength> It was expressed as the value of pole tack resistance according to the ball rolling test method according to J. Don's method.

Example 1 Acrylic acid 2-ethylhexyl ester 60 parts Acrylic acid n-butyl ester 40 parts Acrylic acid 5 parts Acrylic acid 2-hydroxyethyl ester 5 parts Lauryl mercapkun o,t5s Polyoxyethylene nonylphenyl ether 3 parts Water 160 parts Above The composition was placed in a flask No. 11, stirred under an inert gas atmosphere, the temperature of the inner bath was raised to 70°C, and 0.1 g of potassium persulfate was dissolved in 5 g of water and added as a polymerization initiator. Emulsion polymerization was performed. The reaction was carried out at an internal bath temperature of 70° C. for 3 hours to obtain an acrylic emulsion type pressure sensitive adhesive having a weight average molecular weight of 400,000 and a solid content concentration of 40% by weight.

A 25% ammonia aqueous solution was added as a thickener to the obtained pressure-sensitive adhesive to adjust the viscosity to about 50 voids, and then a methylated melamine resin (trade name Cynor) was added to the pressure-sensitive adhesive based on 100 parts of the solid content. 3F0.Mitsui Toatsu Chemical Co., Ltd.) 4 copies,
and 2,2-bis-hydroxymethylbutanol-tris(3-(1-aziridinyl)propionate) 0.
1 part was added and mixed. Next, the mixture was applied to a polyester film and dried by heating at 130° C. for 5 minutes to prepare a pressure-sensitive adhesive tape with an adhesive thickness of 50 μm.

The values of adhesive strength, holding strength, and adhesive strength are shown in Table 1. Table 2 shows the results of similar measurements after one day and several hours in an atmosphere at 70°C.

Comparative Examples 1 and 1' 5 parts of the same methylated melamine resin as in Example 1 was added and mixed to 100 parts of the solid content of the pressure-sensitive adhesive obtained in Example 1 after adjusting the viscosity, and Example 1 Comparative Examples 1 and 1' were prepared by adding and mixing 1.0 part of the same aziridinyl compound, and the same operations as in Example 1 were carried out to prepare tapes. The amount of crosslinking agent in each comparative example was determined so that the initial degree of crosslinking at the time of preparing the pressure-sensitive adhesive tape was about the same.

The values of adhesive strength, holding power, and adhesive strength are shown in Table 1, and the results of similar measurements after being left in an atmosphere at 70° C. for one day and night are shown in Table 2.

Example 2 Acrylic acid n-butyl ester 80 parts Acrylic acid ethyl ester 20 parts Acrylonitrile 5 parts Methacrylic acid 7 parts Lauryl mercaptan 0.15 parts Dodecylbenzenesulfonic acid 2, 5 parts Water lso*
p The above composition was subjected to emulsion polymerization in the same manner as in Example 1, and the weight average molecular weight was 500,000, and the solid content concentration was 42% by weight.
An acrylic emulsion type pressure sensitive adhesive having a carboxyl group of

1.0 part of methylolated melamine resin (trade name: Beckamine MAS, manufactured by Dainippon Ink & Chemicals Co., Ltd.) and Ll'-(methylene-di-p- 0.09 part of (phenylene)bis-3,3-aziridinyl urea was dissolved in 1 part of dimethylformamide and mixed. The mixture was then operated in the same manner as in Example 1 to prepare a pressure sensitive adhesive tape.

The adhesive strength, retention strength, and adhesive strength values of the obtained tape were as follows.
Shown in the table. Furthermore, even when this tape was left at a constant temperature of 50° C. for one month, almost no change was observed in these adhesive properties.

Comparative Examples 2 and 2' Two parts of the same melamine resin as in Example 2 were added and mixed to 100 parts of the solid content of the acrylic emulsion type pressure-sensitive adhesive obtained in Example 2, and Comparative Examples 2 and 2' were prepared by adding and mixing 0.12 parts of the same aziridinyl compound, and the same operations as in Example 2 were carried out to prepare tapes.

The adhesive strength, holding strength, and adhesive strength values of the obtained tapes are shown in Table 3.

Table 3 As shown in Tables 1 to 3, the pressure-sensitive adhesive composition of the present invention has a good balance between adhesiveness and cohesiveness, and the crosslinking reaction proceeds quickly, so it can be used over a wide range of applications. It has the characteristic that a pressure-sensitive adhesive tape with excellent temperature-sensitive properties can be obtained.

patent applicant Nitto Electric Industry Co., Ltd. Representative Sanbe Hijikata

Claims (1)

[Claims] To 100 parts by weight of the solid content of the acrylic emulsion type pressure-sensitive adhesive having a crosslinkable functional group, 0.1 to 10 parts by weight of a melamine resin and 0.0 parts by weight of an aziridinyl compound are added as a crosslinking agent.
A pressure-sensitive adhesive composition containing 0.001 to 5 parts by weight.